Doing this project I put a little puddle of glue on a paper plate and used toothpicks to dab the glue on the pin. First I put glue on the pin just under the glass ball and pushed the bead on it. When that was partially dry, I put a dab of glue on the pin just under the new bead for good measure (I was anxious to continue the project).
I've heard crafters use E6000 glue. It comes in a silver tube. It seems to work well. I bought mine at Hobby Lobby. I'm sure Michael's and other stores have it. Don't forget your 40% off coupon.