Grab bars can add a measure of safety to a shower or tub, but they must be attached properly to insure that they are solidly connected to the wall. Ideally, it is best to screw them directly into the wall studs, but this isn’t always possible. However, you can still obtain a secure and strong attachment by using large wall anchors. See the photos below for a step-by-step installation guide.

An impact drill combined with a masonry bit is an effective combo to drill holes in tile walls.
Carefully drilling well marked holes.
Large wall anchors are inserted and then tapped into the wall using a rubber hammer.
Long screws at screwed into the wall anchors.
A vertical bar was attached in a similar way to the horizontal one.
Overview of the horizontal and vertical grip bars. They will provide secure grab points for the home owner.