It depends on whether the tile was stuck to the floor with glue or thinset. Thinset looks like cement stuck to the tile. It can't be removed without risk of breaking the tile. Use a water proof tile glue and coat the back of the tile and thinset, then coat the floor and thin set. then reinstall the tile in the spot it came from.
When you put it back in place, make sure you put it back in the same position it was in before it came up, or the thinset stuck to the tile will sit on top of the thin set stuck to the floor and make the tile stick up above the surrounding tiles.
Before applying the glue, put the tile back into the spot it came from. If it sticks up above the other tiles, turn it a 1/4 turn and try again until you find the position it sets level with the other tiles. Take a pencil and make a mark on one side of the tile and on the tile next to it. When you go to reinstall the tile make sure your pencil marks are next to each other.
Just purchase water proof tile glue and smear the floor and the back of the tile with glue and put it back in the floor in the same position it came out.
Glue is easy, go to the hardware store and they will have glue removers designed just for this purpose. Remove the glue from the tile and the floor. Put down fresh glue and replace the tile. Refrain from walking on it for 24 hrs.