Grout your walls
Apply large amounts of mixed grout to your float, holding it at 45 °, and spread the grout diagonally across the grout. Start in a corner and work your way up / down the wall in crevices. When you approach the job this way, it will be easier for you to see what you’ve done when you cover a large area. Try to fill all of the lines to the same height, you can remove any overflow from the closet with a trowel or even a knife if you can.
When you’re done grouting, let it harden for about 20 minutes, then take out your bucket and sponge and remove any grout that has spilled from the surface of the tile. Use caution when cleaning the grout as you can remove the pigment from the grout and leave white, colorless stains. If this happens, you can use sandpaper and gently refine the grout until the stains are gone, but do this after the grout has completely dried. Wash the sponge regularly in the bucket to avoid staining the tiles again.
After 24 hours, the mortar should be fully set, but check the bag for certain times. If you have tiled a bathroom, you should not use the shower for at least 2 weeks. This is because they produce large amounts of water that can seep through the mortar, making it soft and crispy, and undoing all of the hard work you just did.