Yes i mean equip the pick axe.

When you first get it, you revert to a lvl 1 miner. and you gain mining experience from doing miner quests and by actually just mining various materials. the higher level/harder to find the material...the more xp its worth. Getting a HQ material gives 200% xp bonus etc.

If you are a lvl 20 gladiator and you just take mining..youre a lvl 1 miner till you get experience mining. Equiping the pick will get rid of ALL your gladiator skills while you are a miner, and you get miner skills on our quickslot bar instead.