Embarrassing question

So I've been open to anal. I'm well aware that you have to prepare yourself and go slow so I purchased anal beads for beginners. Not sure exactly how it goes. Or to even start. I'm shy to ask the people in the shop. I've been using Google. Not sure exactly how to use them. I've read about anal plugs also. Not sure the purpose of those or how to use it but my main question is, last night I used the beads, and now I'm having black diarrhea. Is that from the beads? Is it normal to poop lile that after use? And if you have any advice for toys or anal play or anything please give it to me. Trying to be more open sexually and explore.