I've never heard of using Form 843 for "First Time Abate," but apparently it's a thing.  You can do it with a phone call (if you like listening to music on hold) or with a short letter.  

"How to request First Time Abate
Follow the instructions in the IRS notice you received.

Some penalty relief requests may be accepted over the phone. Call us at the toll-free number at the top right corner of your notice or letter. You don't need to specify First Time Abate or provide supporting documents in your request for relief. We will review your account information to see if you meet the requirements for First Time Abate.

If you choose not to call, send a written statement or Form 843, Claim for Refund and Request for Abatement."

https://www.irs.gov/payments/administrative-penalty-relief#eligible