Tile sizes don't match grid

Right now I’m trying to put in my own tileset, the only problem is that it doesn’t fit the grid. Everything I’ve found doesn’t really help my problem, so I’m asking here. As you can see in the picture, instead of selecting the tile, it selects the corners of four other tiles because the grid isn’t the right size. How do I fix this?

All right I fixed it, now the only problem is that I can’t place the tiles.

To place tiles:

  • Make sure you have a tile layer selected (add one if necessary).
  • Make sure you select some tiles in your tileset.
  • Make sure the ‘Stamp Brush’ is selected
  • Click on the map, making sure you’re painting inside of your map (turn on the grid if you’re unsure where the map ends)