I'm actually struggling to think of a way to describe this succinctly...
I was pretty much just being cheeky and alluding to the fact that you were going to use your likes to curry favours and add girls to your waifu collection. Typically the term is bandied around by weaboos (anime fans) to talk about the fictional characters they would marry. However, it is finding it's place more and more among everyday slang as a way to say that you like someone and would jokingly marry them. Here is an example from the other day.
Me: That smells really good Lila.
@Lila36 : is microwaving food Oh I made it myself.
Me: Be my waifu plz.
Me: I really like Sephiroth.
@Vexx : Would you say he is your waifu?
Me: He is my husbando.
This has been your lesson on animu culture for today.