Enchant creature
At the beginning of your upkeep, you may put an arrow counter on Archery Training.
Enchanted creature has "{T}: This creature deals X damage to target attacking or blocking creature, where X is the number of arrow counters on Archery Training."
If there is more than one Archery Training on a creature, each granted ability counts the counters on the Archery Training that granted that ability.
Putting on a counter is optional. If you forget, you can’t go back later even if it is something you usually do.
You do not remove counters when using the ability.