advertising help

I am getting ready to release a new channel in the next couple day's and have not been able to find straight answer's to my question's anywhere. Even though this channel has not been released yet and has 0 subs, we are fortunate enough to have a brand donate product to us. We no that we have to...

I've read that there are great websites for advertising my Youtube channel such as Facebook and Reddit, but where would I advertise within these sites. Also are there any other good sites to advertise? Any help would be greatly appreciated as I want to be able to reach the biggest audience I can