Speak with Julia Sunstriker - the Mage class trainer - inside the Sunspire on Sunstrider Isle.
As you advance within your class, you will want to take advantage of the training that your class trainer can provide you. For young mages here on Sunstrider Isle, your trainer is Julia Sunstriker. Speak with Julia and see what training she has available for you. The things she will teach do have a cost, so bring some coin with you.
Julia - as with all the trainers on Sunstrider Isle - is inside the Sunspire on the lower level.
Ah, <name> - I believe you're one of the new mages here on the isle, yes? Well, you've come to the right place. If arcane mastery is what you seek, then I can provide such knowledge - as long as you have the wherewithal to handle training costs and the capacity to focus on the lessons I'll be teaching.