So the directions for a buttonhole I can partly understand, but when it tells me to slip one as if to knit, I´m not sure what that means. Does that mean slip the right needle in as if I´m going to do a knit stitch?
Yep, you got it! 
When you slip a stitch, you are just moving it from the left needle to the right needle without actually working the stitch. When you are instructed to “slip as if to knit” you are inserting your needle as if you were going to knit the stitch, but you don’t actually knit it … you just move the stitch from the left needle to the right one.