You can open an account at your bank, or online by yourself, or through an agent.

Bank and agent require commission fee. I used to have an account at my bank, paid $35 yearly.

Then I openned a Roth IRA account at www.fidelity.com and transmitted all my Roth IRA money and funds to that account. No commission fee, no yearly fee, very convinient, and friendly and helpful customer service. No boker needed.

Once you have a Roth IRA account, you can deduct money monthly from your checking account to put into this Roth IRA account. You can use this money to purchase whatever you want, stock, fund, etc. My suggestion is to buy funds. If you want, you can use fidelity.com's research tool to browse different funds. I am lazy and don't want to shuffle the funds myself, so I bought the FFTHX fund, which is a combination of different funds, and aimed for maturity in the 2030's. 

Depending on the funds you buy, you may or may not need to pay fee for the funds themselves, besides the yearly Roth IRA account maintenance fee. Of course, if you buy from fidelity, most of their funds are free of fee, and their account is free of charge.