Gas Additives to Prevent Gas from Varnishing

hey- I've done a search, and although I'm sure this is an easy one for ya'all it ain't so for me as I'm brand spanking new to this.

My kid and I are gonna be riding indoors this winter, but only about one weekend a month, total ride time 4 hours. We won't be starting or riding our bikes in between. I've heard I can add something to my gas to keep it from clogging the jets sitting around and getting old. I can't the doc find where I read this before, but was told I could get it at napa or someplace that mightbe open on Sundays.

We don't have access to bike shops mon-fri because of my work schedule, so you are pretty much my last bike knowledgeable resort here.

Help someone, please?

Thanks in advance.

I was afraid someone was going to tell me to drain my gas, blah blah between rides. And knowing I can find it at a store that caters to my work schedule is a double god-send.

Thanks so very very much!!!