You don't say whether these are multitrack or not, but the following should get you started.
You want to look up the Export Audio function in the documentation. You can export parts of the long file as individual shorter files. You can then Import these into the same project, or a different project. The basic idea is:
1. Select all tracks (ctrl-A), assuming you want to export all the tracks you recorded.
2. Click at the beginning of the individual song in the timeline, and drag to the end of the song.
3. Choose File > Export > Audio. The Export menu presents lots of choices, you will need to look at the documentation. Or, just go with the defaults, which are what you want 95% of the time anyway.
4. When you want to bring the exported file into a project, locate it, place the Now time where you want the imported file to start, then choose File > Import > Audio.