Do I have this right?

So tell me if I have this right..

I have 400 shares of BJ’s Wholesale Club trading at $60 right now. If I want to sell puts and collect the premium I can sell 4 contracts (400 shares) at anything below $60 and if the stock price doesn’t fall below the strike price I keep the entire premium, right?

So for example I could sell 4 of the Feb 18th puts with a strike price of $55 for the bid price of $0.30 and collect $120 in premium right?

Now what would happen if the stock price does go below $55? I would be required to buy 400 shares at the strike price correct?

Thanks for the help.