How do I make Time Machine automatically delete some of its files before it gets full?

Time Machine will automatically accomplish deletion when room is needed for a subsequent backup. According to Back up your Mac with Time Machine, "The oldest backups are deleted when your backup disk is full."

If this is the case as I see it the options are ;

1 - Get a New Drive with at least 2 1/2 x Larger Drive Capacity than the existing Internal Drive and set it up as the New Destination

2 - If going this route - suggest putting the existing Drive in a Safe Location ( Safety Deposit Box of Bank ) incase it is needed in the future

3 - Reformat the existing Drive - this will erase all the TM Backups - and start again

Was it referring to this drive or your internal drive where snapshots are made and stored? How much room on your internal drive do you have?