What sort of help are you looking for? And where are you looking to do this (makes a difference)?
Ideally, you’ll have checked to see if it’s feasible (i.e. it’s not like there are 100 such businesses where you plan on doing business) and that you have the cash to cover the possibility that you might not have work for months.
Then you should set up the business entity (the easiest is a sole proprietorship in the US since you can just start doing business day one like this…the drawback is you can be sued for your personal assets if someone wants to).
After that, you’ll need to just get out there and find work. Cold calls, hitting the pavement, or contacting trade associations for contacts are what you’d likely need to do unless you’ve got a nice sized network of contacts to pull from.