How do I grout the floor tiles ...

This applies to single colour tiles only, we do not recommend grouting of the 2 colour or octagonal tiles. 
Once you have finished laying all your tiles you will need to seal them before you begin grouting, this is to prevent the colour from the tile mixing with the grouting. To seal the tiles you will need a mixture 1/3rd PVA glue to 2/3rd water, mix well and apply to the whole floor with a small artists brush. Once dry, mix a small quantity of grout mixture with water until it is a nice creamy consistency. Apply the grout mixture with a damp cloth in a circular motion, small area at a time ( 3" x 3" ), then remove the surplus grout mixture using a clean damp cloth. Continue the same process until you have grouted the complete floor, leave to dry.