Wear eye protection for debris as well as for ultra violet rays from the hot metal. These emissions do cause cataracts.
Find out what all tools you need and if the forge is in compliance with the local regulators. The tools will vary depending on what you wish to do.
Get some books about iron and quenching and heat treating and annealing and about forges and anvils Etc.
Find some shops that scrap iron bins for some supplies.
Get metal toed leather boots and keep them laced right to the top. Pants that go over the top of the boots. Wear cotton/wool clothing. No nylon. Some good gloves. Leather apron.
Do a google search for information as there will be a lot out there.