Use tile adhesive to stick the tiles to the surface, then when completely dry use a grout to fill the gaps between the tiles. Various types of adhesive and grout are available.
Ready mixed adhesive/grout is less hassle, less messy, a bit more expensive, but dries quite slowly. I tend to use it on small jobs, for which you can buy a combined adhesive and grout which saves buying both.
Powdered adhesive which in my view is much superior(used by professionals) is mixed with water, dries very quickly and doesn't slip so much when wet. A bit more messy for mixing and cleaning up afterwards, but it is very hard wearing.