P. Meaning "Pick".
Maybe it's time to read some manuals?
Use the p key for pick
Use the x key for reject.
It’s a quick way to cull your keepers and those you may want to delete.
After deciding on your picks, it’s a good idea to apply star ratings. These can be saved in the files (embeded) unlike picks and rejects.
And the beginners key shortcut- CTRL+/ CMD+/ on a Mac. (that is CTRL + the key with the question mark above the forward slash)
The shortcuts in this window refer to the current open module.
Don't forget u for Un-pick (remove any flag)