What you do is you make a tileset that has to be 320 pixels wide and some multiple of 32. Each 32 pixels in the image is one tile, after you complete the tileset(256 color bmp or pcx) and the mask(same size, also 256 color bmp or pcx) then you can compile the set in jcs by pressing the 'set...' button and then the 'add set' button, fill in the information, the tileset is the tileset tile you made, and the mask is the mask file you made(They need to be in the \Tiles folder)