To install a shelf on a tile wall you'll need to anchor the shelf to the wall using some wall anchors and a drill bit made for drilling through tile.
Go to home depot or other hardware stores and look for a drill bit to drill through the tile and then you also need some screw anchors that insert into the hole in the wall that you drive the screws into.
When drilling the tile take your time and let the drill do the work and don't force the drill otherwise you may crack the tile.