Configuring Wildcard Subdomains – Hosting Company Can't Help?

I’m out of my depths when it comes to doing things like this :

I have the subdomain feature working on the website, everything loads fine etc, but when it comes to typing /wp-admin after the subdomain so a user can log in, it stops working. It just hangs for ages.

Seems to be stuck in some sort of redirect loop, and APPARENTLY, following those instructions in the codex document above. I can barely understand them though.

Suggestions? Please haha.