First, please check if the bell of your saxophone fits properly into the padded fork. As it is right now it will fit most Alto’s and Tenors nicely, but there are always exceptions to the rule.
If it doesn’t lower into the top bracket as far as you would like, you could gently pull it apart or push together a little by hand. Do not put in a vice or use tools on it since that could damage the stand.
Furthermore you should decide how you want your instrument to be positioned. You could sort of hold it up in front of the wall with your instrument in it in the preferred position, have someone else mark the holes and mount the stand accordingly.
Especially with drywall it is of utmost importance to find a spot that offers solid footing for the screws, and has a stud or beam directly behind it. For stone walls you will have to drill holes with a ¼ inch drill bit and insert the wallplugs and screws. The little caps are to cover the screws. Put hem on the tip of your forefinger and place them over the screw’s head. Then, with a twisting movement of your finger feel for their proper position over the slot, then just push them in. Use some glue if all else fails.
If you use a cordless drill for the screws, make sure its chuck doesn’t damage the coating.
If for some reason you are not sure how or where to mount it, please contact us or get some professional help!
To keep the rubber in good shape you could occasionally very lightly spray it with silicone and rub it in.