craftgrrl | attaching straps to a plastic bag?

Hi, this is my first post in the community. I'm a rather new crafter- I never knew it was my calling until I started knitting this summer, and realized I was really into creating things. i don't have a digital camera, unfortunately, but it's on my christmas list so hopefully i'll be able to post finished projects here someday <3

We split into groups in math today, and my super-generous student teacher gave us group a huge shiny new bag of M&Ms. i ended up with the bag and about a pound of M&Ms. i decided i want to keep them in my locker, but that wouldn't be very practical. the bag is lovely and christmas-y, so I decided that the only sensible thing to do would be to make the bag into a purse!

problem is, I have no idea how to attach straps to it.

it's made of some sort of shiny plastic, and has a resealable zipper top... i don't know if i should sew straps on, or staple them or something. i also have no sewing machine...

can anyone help?