Or you can use online form. Sorry typing English.

you may also do it by yourself.

Depend what you need.

Just register a business. A sole ownership unlimited liability business can be just a dba in county record office (cost least). An LLC or S corp can provide more protection but cost more. Should register in state level. Before you register, you may need to know the requirement, benefit and liability. (reporting, tax, etc)

If you cooperate with another person. (even he/she is your spouse), you may need to hire an attorney to have an operation agreement to prevent future problem.

If you are in Texas, you can google Texas SOS. Can find a lot information.