Hi there!
Most cruise ships dock at Sitka Sound Cruise Terminal, but there are also cruise ships that anchor offshore in Sitka. In this case, the cruise ship will anchor off of Crescent Harbor or O’Connell Bridge, making Sitka a tender port for you. From the cruise ship, you’ll take a small boat (tender/water shuttle) from the cruise ship to get to land in Sitka.
The small boat will drop you off at either Crescent Harbor near Harrigan Centennial Hall, or right under the O’Connell Bridge near Baranof Castle State Historic Site.
You can check the official Sitka cruise port schedule to determine where your cruise ship will be anchoring.
If you’ll be tendering on a mainstream cruise line (and don’t have priority status or a cruise line excursion booked), then it’s very important that you pay attention to the tender instructions you’ll get the night before in the daily activity schedule. Tendering from a big cruise ship can take a long time. You need to go to a certain spot on the cruise ship in the morning to get a tender ticket to get off the cruise ship. The earlier you’re in line for that, the sooner you’ll get off the ship!
I was on the Norwegian Sun cruise ship, anchored in Sitka off of Crescent Harbor. This cruise ship has a passenger capacity of around 1,900 passengers, and it was an end-of-season cruise so I’m pretty sure it wasn’t a full ship.
The official arrival time to Sitka was scheduled to be 11:45am, and it was listed on the daily activity schedule that you could get tender tickets starting at 9:30am at a designated location on the cruise ship. I got in line to get my ticket right around that time. My ticket placed me in group 6, so I waited for the public announcement for my group number. I got on the tender boat at 12:43pm, and I go on land in Sitka at 1:01pm.
So even with following the instructions, it took me over an hour to actually get started walking around Sitka from the official cruise ship arrival time in Sitka. You can see more about the cruise ship tender process with pictures.

You can know where your cruise ship will be anchoring by checking the official Sitka cruise port schedule. If it says a number with CR or BR next to your cruise ship, then it means that Sitka is a tender port for you, and you can determine where your tender boat will likely be arriving at Sitka.
CR = anchoring off Crescent Harbor, with a likely tender to Crescent Harbor
BR = anchoring off the O’Connell Bridge, with a likely tender to the bridge
If you see STI or STO, it means your cruise ship will dock at the main Sitka cruise port of Sitka Sound Cruise Terminal. If you only see SIT (Sitka) and nothing else, then check back once your cruise season is closer.

A tender boat to the O’Connell Bridge will drop you right under the bridge. You can find it on google maps listed as O’Connell Bridge tendering facility (map).
From here, you can walk 5-10 minutes to get to Castle Hill (Baranof State Historic Site), which is a nationally significant landmark. It’s the spot where Alaska became a part of the United States, having been sold to the US by Russia. (Sitka used to be the capital of Russian America.) Then you can walk another 5-10 minutes to get to the main area of downtown Sitka.

Look at the O’Connell Bridge tender drop-off on google maps.

Spot the bridge!
A tender boat to the Crescent Harbor drop-off will put you right near Harrigan Centennial Hall, which is an easy way to locate it on google maps (map).
Start your time here by walking into Harrigan Centennial Hall where you’ll find paper maps and the Sitka History Museum for your intro to Sitka. Then, you can walk around 15 minutes along Crescent Harbor and the seawalk to get to the Sitka National Historical Park visitor center to do the totem trail. Along the way, you can stop by the Russian Bishop’s House (national park rangers give free tours) and Sage Beach (see if you can spot any marine life on this little beach).

Look for the Harrigan Centennial Hall, and right near here is the Crescent Harbor tender drop-off. See it on google maps.

I had a tender boat drop-off at Crescent Harbor.

You’ll take a small boat from the cruise ship to get to shore!

My cruise ship’s last tender back to the cruise ship was 45 minutes before the official Sitka departure time.
Read: Alaska cruise excursions you need to know about
I've picked out a theme for each port so you can experience different aspects of Alaska!
Or go straight to my picks for booking tours independently in Alaska cruise ports!
Explore Alaska cruise ports:
Juneau | Ketchikan | Skagway | Icy Strait Point | Sitka | Victoria
Seattle | Vancouver
Whittier | Seward
Things to know: Mendenhall Glacier on your own vs shuttle
PACKING LIST: waterproof shoes | rain jacket or poncho | puffer jacket
Before you book: First-timer's guide to Alaska cruises