My first Red wine from grapes

[Nobbynormal]

hi, I was given about 20 kilos of over ripe, some mushy grapes last week. I crushed them and strained them the next day (got about 2 gallons of juice) but had no yeast so left them till now.
I brought them indoors last night to get to room temp before adding the yeast but the must has started fermenting quite vigorously overnight.

My question is, should I add the Gervin wine yeast or leave it to naturally ferment.
Thanks.