I use the trial version of Lumapix. It's userfriendly, fun, and free.

First, Go to lumapix.com
At the very bottom of the page, click on downloads.
I'm using the free trial version, I'll purchase the program when I want more options, but for now I really like this one. I like my collages simple that won't take away from the photos. To use this one, download lumapix Fotofusion 3.7 version, not V4 version.
Then click on Auto Collage.
To upload your pictures, get in the right folder by clicking on the small square next to folder, then click on browse. (Is this where you where stuck Rony?)
Once you've selected your photos, make sure they're right side up and click on next.
Now, make sure you change the canvas size to 10" x 10", this will prevent Luma pix watermarks all over your collage.
Then click on finish.
Click on process to save your collage, name it, and save it in the right folder.

Well maybe not super easy at first, but once you play with it you get the hang of it fast.

Few more tips:
-no need to crop your photos beforehand, you can zoom in and out, rotate, tilt, etc. while creating your collage.
-use auto tools to change order of pictures on your canvas. You may delete and add more pics if wanted.
-double click outside of canvas to add text.
-when/if you purchase the program, their are many more options.

BTW, if you purchase this (reasonably priced), I suggest going through Donna at Double Happiness, she referred the program to me... She's the real pro!