First of all i liked your design..but don't like your header..
Ok to setup a forum like this,you will need to buy your own hosting.
I would suggest you to use hostgator..personally because i have used many many hosts and is now addicted to hostgator..
They provide me unlimited space and bandwidth at 100$ a year..
If you plan to use hostgator,just buy the hosting and ask the hostgator guys to setup a cname record for threebrothershealth [cname record pointing to ghs.google] they will do that in advance if you ask them to do so..
Now just point change your domain name servers to that of hostagator.. [Nameservers are something like NS6876878.hostgator]
When you are done with this,your main blog will be still hosted with blogger..you will need to create a redirection from threebrothershealth [just create an htacces file to do this..]
ok now add a subdomain from your hosting account.. a subdomain like forums.threebrothershealth .
In the root directory of the subdomain download and install BBpress
Its the s/w that powers this forum.It is completely free and Opensource. Its another great thing from Automattic,the makers of wordpress.
You can also do the same with godaddy hosting if you have got one.But i would personally suggest hostgator..
If you plan to use hostgator ,and if possible use my referral link
and also search for some hostgator coupons before you signup.. you will get some discounts..
If you need more help feel free to contact me..