Ok, so I have done the basic knitting for a purse but now I have to simply “sew sides together”. Does that mean using the mattress invisible stitch? (Doesn’t that take forever to do?) I know I don’t want the whipstitch on this. I am not supposed to sew like on a sewing machine, am I? Gee, the finishing is not as straightforward as I thought it would be!! Thanks for answering!!
I usally just use whatever stitch suits me with the yarn that i have been using to create the magic! 
you can check out the finishing techniques here (scroll down) and see if one of them suits you. 
The matress stitch will give you an invisible seam!