.. What should I do in Frank's apartment?

Now that you know where the apartment is, go there and have Rosa use the paper clip on the door --

-- and break it. Damn! Well, send Joey in, then.

There are lots of rather sad things to look at here, but the thing you want is on the kitchen table.

Look at the script to find out what responses Frank wants from Rosa. After Joey tells Rosa about the script, this page is an item in her inventory, in case you need to refer to it again.