Two ways in, and you can use either or both.
Paste your library. This is the only way that brings in
family-shared games, since Steam hides those from everyone but you.
- Open Steam and click Library.
- Click the first game in the list, hold Shift, and click the last one.
That selects the whole list.
- Drag the selection into an open Notepad or any text box.
- Copy all of it and paste it below.