Clear stamps are very easy to use; simply peel off one or more stamps from the clear sheet and place them on a clear acrylic block. The stamps will cling to the block and you can then apply ink to the stamps. Keep a firm grip on the acrylic block and position it over the paper to be stamped. Apply even pressure and use a stamp pad for the best result. Lift the block straight up to avoid smudging. Clean the clear stamp (alcohol-free baby wipes are an easy and fast option, but water and mild soap will work just as well), remove it from the block and place back on the clear sheet and they're ready for your next project!
Definitely. You're free to incorporate the stamps in all of your creative projects, both personal and commercial ones. What you can't do is copy/recreate the stamps, repack the stamps in other packaging with the intent to sell or attach the stamps to wood, plastic or other material and sell as a new product.