Can anyone help me with estimated tax for self-employer?

I got a mail from IRS, but it's at my old address. I will pick it up tomorrow. I had no idea what it's about at first, but the envelope says it is about 1040-ES.

 

This may sound stupid, but I didn't know that I was supposed to pay quarterly tax to IRS as a self-employed taxpayer. I just started filing tax as a self-employed last year, and I didn't even know there was such a thing.

I am about to file my tax for 2020, but what if IRS asks me to pay the quarterly tax+ penalty first? it will mess up with the calculation of the 2020 tax filing. What should I do? Any suggestions?

 

Dang, this is a huge headache to me. I am afraid of how much they would have charged me for the penalty.