Then you just grout.
I worked in small spots, this makes it easier to get into all the lines I need.
You just need to use your finishing trowel to put it on and flatten it out.
I used pre-mixed bright white grout, however, you can use whatever kind you want.
Make sure you follow the directions on your specific grout you have.
I used a wet sponge every so often to wipe off the excess grout and smooth it out.
Soon it will all dry and look great!