Click on the wall on which you want to add the tiling. In the properties panel, click on the Wall Section tab and go to the resulting panel. Click on the Tiling and Cutting Tool option. You will enter a mid-state where you will be presented with the front elevation of the wall face. Click on the Add option in the upper ribbon to enter the Sketcher mode.

Once there, draw the desired shape of the tiling, go to the Tiling and Cutting panel and click on Apply to save changes, or Discard to ignore those changes. Then click on the Back to Designing arrow at the top right corner to finalize the tiling.