Just dab ink onto glossy cardstock. Get it on there any way you like; smoosh the ink pad directly, use sponges, solid stamps ot the acrylic block itself. That's what I did with my first two lighter colours. The third and darkest colour I added with a sponge, just a bit, here and there. Then, emboss and sand. If you sand too far, just add more ink and sand again. You can't mess this one up, can't do it wrong and can't help but enjoy the process. At least, I hope you do.
Take a minute and give it a try today. :)