Looks like it’s already started to be shaped for a semi cascade, dunno about a full cascade yet the first question to be answered is, “Is this tree suitable for bonsai?”
So a couple ideas.
1. Get the tree healthy. It looks like it’s just holding its own. Be sure it’s watered regularly and start fertilizing it regularly. I’d try something like a fish emulsion and humic acid every other week and sprinkle on some Osmocote plus... to get it going and see if it will start livening up and back bud.
2. Find out what type of tree this is. You can post a thread here requesting identification to start with or go to a native plant nursery and see if they can help. Once you know it’s identity, you will be able to get information on if it is bonsai able.
cheers
DSD sends