Dremel query - urgent!

Hi, all.
A really basic question: How do you use the sanding bits for a Dremel? I slip them onto the rubber cylinder, but they don’t grip it at all, and when they come into contact with the object to be sanded, they simply spin around.
Greatly appreciate any help!

Their should be a screw with a washer on the rubber drum. After putting on the sand disks just tighten the screw. That compressed the drum forming a tight seal. The type that have an adhesive backing on them that fit on the flat disk, just press down on the disk. If the rubber disk is dirty they will not stick so wash with windex and let dry. This type will not take a lot of pressure.

THANK YOU, Berny!