Set Preferred Network Type For 5G Phone Question

I just started using my new at&t prepaid wireless unlimited plan on my LG Velvet 5g - Model LM-G900UM android phone today. As my new phone is 5g capable, I was wondering what the 'preferred' band should be set on so I could utilize the 5g network that is available at my location. I have a google play store app installed on my phone that lets me manually choose which preferred band I'd like to choose. There's a pretty long list of band's that are available so I surely wouldn't want to choose the incorrect network setting. I currently just have it set on lte only, I don't think that 5g is available by using this setting. Can someone offer me some information about this, thanks in advance for your help.

David