I don't know if there are tutorials anywhere...I just kinda started out by winging it and learning from my mistakes For wall canvases, I will either cut a piece of paper and used mod podge to glue it on or paint the background. Paint looks neater b/c with paper it is hard to cut it exactly and sometimes the canvas isn't quite even. Also, the paper sometimes gets bubbles underneath if the mod podge dries a little before you can stick it down.
Once you have the canvas painted or however you decide to do it, use mod podge on the back of the cricut cut out to adhere it to the canvas. Once you adhere all the paper cuts, then I put a coat of mod podge all over to seal it. You can do a second coat if you want...sometimes I miss a couple streaky spots and have to go over a few little places, if you know what I mean. I always use the sponge paint brushes to apply it.