Alternating which partner is active, or having both partners be active, can help a couple to become closer to each other and help them understand the full range of their sexuality. If we only ever are active or passive, we will never understand the whole range of our sexuality as we will cut ourselves off from parts of it.
You will train him to associate anal sensations with sexual pleasure because that, once a man experiences the sensual pleasure that anal play can bring, he’ll allow you to explore the possibilities a little further.
Given sufficient time and patience, he will eventually allow you to take it to the ultimate step of full anal penetration with a strap-on dildo.
If you have decided to incorporate the pegging to your relationship, don’t rush. Choose the best moment to tell him; a moment when he is very excited and receptive.
Tell him you want to fuck his ass in the next months. Be very sexy when exposing your idea and take profit of that excitement to negotiate with him. Deal and establish clearly the limits, changes and punishments, also the physical ones, which you will apply if he decides not to obey at some stage.