How do you "Join" swatches of yarn?

I have knitted up 2 skein of yarn in garter stitch for a lapghan. But they are in two different yarns I want to “patch them” together (kinda like a quilt) to make the lapghan bigger. how do I do this?
thanks

Go to Finishing on the advanced Techniques page. You’d seam them together the way you would if you were making a sweater.

sue