How do you

How do you narrow down the ATG 9 set into a smaller subset? Say you just wanted a pool of players from 1970 and later or only players from the 1800's?

Go to INFO/HELP on your top menu bar, on the drop down, go to PLAYER SET BROWSER.
Download the spreadsheet (there is a link)
Open it in Excel.
Delete the players (by deleting the row) that you don't want in the subset.
Name and save the subset, then see Kev's note below.

the above is correct but you upload to Strat vs sent.

in the menus see 'community' > 'custom players sets'

Sounds confusing but I will give it a try. Thanks for your help.