Hosting a web page?

I am new to hosting a site on my servers. I have the page done and loaded into web server software and users internally can access the site. I am looking for information on the process of getting your webpage to be accessed from the outside, DNS setup from ISP, IIS settings, etc.

I already have the site being hosted by someone else and have the domain name registed and pointing to their DNS servers, so I know part of the process is getting the register to point to my DNS, but I need to knowhow to set that up on my side. Any thoughts, links, process’s are welcome. I would like to see an example from the beinging if possible.