More agony resistance from infusions

With Fine Infusions such as as Precise Infusion, you just double-click it and apply to the ascended ring, right?

However, can you add more infusions to the infused ring which results to +10 AR (+5 & +5)? Is it possible? I'm asking this because I'm wondering how people got 40+ etc. AR. How can I get more agony resistance? Is there a maximum AR for each accessory?