If you don't already know how things work, take this chart, put three characters with a common theme on here, and either draw or request someone else to draw fusions for the chart. A fusion already exists for two characters? If you don't feel like drawing your own version, just put that fusion up on the chart. Otherwise, go nuts. The only real limit is to keep the chart related to /co/.
If you feel like keeping them somewhere other than the archives, just use the /co/ booru: https://the-collection.booru.org/
So, go ahead. Fuse your waifus, husbandos, or what have you. You don't have to do anything complex for them. Just stick to the themes and have fun.