Translation of a tutorial I made some times before.
-Download cluster sprite tool and put it in the folder your game is
-Download a cluster sprite. There should be 3 files, a .asm file that is the cluster sprite and a .cfg and .asm file that are the custom sprite that generate the cluster sprite (you can't use the cluster sprite directly).
-Put the cluster sprite in the csprites folder and the custom sprite in the sprites folder
-You know in spritetool you need a .txt file with all your custom sprites listed? Well for clusterspritetool, you also need to have a .txt file with all the cluster sprites. Exemple of both lists
-Before inserting, open the .asm file of the custom sprite and find the place who say which number the cluster sprite is. Change it to the number you put the cluster sprite in your list. Exemple
Open clsptool.exe and enter the rom name and the cluster sprite list name. Exemple
Then use spritetool and insert sprite like you always do. Exemple
And so it's inserted. Put the custom sprite that generate the cluster sprite in your level now.