Fisk wasn't in my retired player pool - he was just never imported. To check your retired player pool, go to the menu for your league (mine is called "ML"), and select History. You'll see a tab for "Retired Players" there.
I've just been looking through the manual, but I can't figure out how to import a single player from the Lanham database so that I can add Fisk manually right now. Does anyone know how to do that? Otherwise, I'll have to change his debut date to 1974 and have him get imported along with the rest of the rookies next year.
EDIT: Never mind - I found it. It's on the Free Agents page, assuming that you're a commissioner. There's an "Import Historical Player" button there, and then assuming you know the player's database id (see
Baseball-Reference.com - Major League Baseball Statistics and History), you can import him and assign him to the team of your choice.