Tile Cement and Grout at tile shop along with a spreader. They will be able to answer your questions.
Ask the pros at the flooring dept. of your home improvement store...take some good photos and the room dimensions.
Here is a DiY https://www.hometalk.com/10530891/diy-how-to-install-floor-tile
Watch installation videos on YouTube.
Measure even lines to place them straight put them right up against each other