Sl1yib?

I am doing a pattern and it calls for a SL1YIB which I understand is a slip 1 stitch and yarn in back. Do I slip the stitch then put the yarn in back to to do the next stitch which happens to be a purl or do I put the yarn in back before slipping the stitch?
Thanks for your help in advance!

:happydance: Your going to put the yarn in the back and then slip oneā€¦:thumbsup: