problems with Forwarding to different Host

Now I have done a search and found variations of the questions but no clear answer.

My site is blogmd.net which I acquired through yahoo domains.
I am forwarding the site to my host site https://s87145207.onlinehome.us/

So when I enter blogmd.net into the address bar its working fine. But when I enter https://www.blogmd.net I get an internal error with not being able to find the site. Also all the permalinks on the site have the Host address (https://s87145207.onlinehome.us/) and not the blogmd.net address. My aim is to make the end user unaware of who my host is. I want them to only have to deal with Blogmd.net and never have to see the full address. Also when I go from blogmd.net and click login and enter the correct name and password all it does is redisplay the login screen. If i go from my original host address it allows me to login just fine? Why is that?

Now I realize I may have to change some things with my yahoo domain so I wanted to find out what things I need to change? Yahoo domain offers forwarding as well as an ‘A’ name and ‘cname’ service. I am not sure what these are? I appreciate the help.