You find the tourist office in the building of the ferry terminal on the city center side. They have a free city map which has the information in Polish/German/English. The sights are listed on the back.
The proper address of the tourist office is:
Tourist Information Center
ul. Wybrzeze Wladyslawa IV
(near the "Centrum" ferry port)
phone no. +48 91 322 49 99
Just a short transportation tip...
because we were sent back again and couldn't see much of the city.
The border between the German part of Usedom island and the Polish part used to be open for cyclists and pedestrians only. On the German side there were large parking lots, where you could leave your car for a fee, and on the Polish side there were rows of taxis, to take the tourists into town.
Then, with Poland joining the Schengen area, the border was opened for cars as well, savings travellers a detour of about 250 km. There is a ferry in the city center, well-marked and shown on the city map.
We were going to take this ferry, but when it was our turn to drive onto it, we were told that this ferry is for the citizens of Swinoujscie only. So we had to go back. I later learned in the forum that this is a ferry for commuters, and only on weekends it can be used by non-citizens. We should have turned right , to get to another ferry, open for anybody.