To give a sticker you must open your album and select the sticker you wish to give, for example the Avocado as in the image below.
Click on the orange "Send to a friend" button (indicated by the red arrow in the image below)

The panel with the list of all your friends will open:

Click on the green "Send" button on the right of the friend to whom you want to send the sticker.

You can give a sticker every 24 hours to the same friend but you can give as many stickers as you want to different friends.

If you have many friends, to immediately find which one you are looking for, you can write his (or her) name (or the first letters) in the black bar (indicated by the red arrow in the image below) and you will only be shown the nicknames that begin with those letters

If, instead, you want to give it to a member of your Club click on Club (indicated by the red arrow in the image below)

Now click on the green "Send" button on the right of the Club member to whom he wants to send the sticker.
If your Club is large to find the Club member you are looking for immediately, find it as explained in the previous point for friends.