Depending on which method of installation you choose, this question can be answered differently. As already mentioned, you can attach the shower caddy to the wall with screws. This method requires a bit of dexterity and you will need a drill. It is easier to simply glue the shower caddy to the tiles.
This option is also available. In your search, you must make sure that the shower caddy is for gluing. But it always says so. It is even easier to attach the shower tray with suction cups. You simply stick them to the tiles and can always move them to a different place, depending on your needs. This is an advantage over other methods.