how to backup an iphone thats never been backed up on icloud

I have had my iphone 6s for a couple of years now and recently decided to upgrade to an iphone11. Apparently, I never backed up my iphone 6s to icloud. I am now trying to do so, but have been unsuccessful. I want to back up everything on my iphone 6s so that I can transfer it onto my iphone11. If you could break down how to do it step by step, I'd greatly appreciate it.

"Why don't you explain this to me like I'm an 8 year old. ...Why don't you explain this to me like I'm five." - Michael Scott

Thank you in advance