1) go to the users profile
2) either click "give props" underneath their profile information or go to their wall. you can also click on one of the prop symbols- many ways lead to rome on this one!
3)click on the grey prop symbol (see image) to open all available props
4) write a personal message
5) choose the appropriate prop and click "post"
You mean give someone a prop for a video, comment, article, etc.? Just go to the person's profile, click on "Give Props" (left-hand side of the profile page, in the "about me" section), then click on the type of prop you'd like to give. You can also add a comment, explaining what the prop is for, at the same time.