Take knife, get some peanut butter. Now, in your other hand, take the spoon you were going to eat the ice cream with, and use the back side of it to ... wait for it.... scrape the peanut butter into the bowl.
I hope you were not going to mix them together, because at this point its a bit too late to eat them separately. I apologize... I ought to have warned you this might have happened beforehand.
But really, just dump it in there, mix it in, call it good. Add maple, caramel or chocolate syrup if you need it even sweeter.