The groups folder is located in Gloss's data folder (Gloss/groups). In this folder, by default, it will contain a help.txt file explaining different parameters you can use.
Simply duplicate either the _op.yml or member.yml and rename it to your permission group name you wish to add to.
# Modifies the player's tablist name# I.e. &7cyberpwntablist-name: '&7$player'# Show a specific board for this group upon logindefault-board: member-board
Simply save the file and use /gloss reload.