How Do I Sl St a Seam?

I am working on a lion brand pattern for a wrap scarf w/ hoodie. It says that I have to fold it in half and sl st the seam. How do I do this with a yarn needle?

Thanks for all your help!!!

[FONT=Comic Sans MS][SIZE=3][COLOR=darkorchid]Don’t think I’ve ever heard of this being done with a needle. You can do it with a crochet hook…[/COLOR][/SIZE][/FONT]

Thanks for the Help!! It was exactly what I needed!!!:happydance: