i cant get my stickers to work in imess

I have downloaded the sticker app stipop and I can’t get their and some of my other stickers to work. When I drag them up to put in the text bubble they don’t stay. The ones that have a keyboard too will work. Online it’s saying hit the App Store icon and a group of 4 dots will show up and activate through that but when I click on App Store I don’t see those dots. I have the newest update iOS13 and my phone is a iPhone XR and when I downloaded the app it said it works with my phone. Please help.