How to get one?
Go to a Tesla showroom and buy one,that’s it. No tesla’s on motability so if that’s what you “need” (not sure why you need a Tesla and nothing else but that’s your business). You’ll need the deposit, monthly payments, pass the credit check then need to budget for all the usual like insurance, servicing, tyres etc.
If you want to use the scheme then you need to look at what’s actually available by searching, there are lots if low cost ev’s on there that are arguably better than the tesla in some aspects at least.