Hello MC Black, no problem. I'm sorry, my reply was a bit on the brief side. Here are the steps:
1) Type 'about:config' (without quotes, as one word, no spaces) in the URL (web address) bar and hit return.
2) Confirm that you'll be careful.
3) Type 'newtab' in the search field (this will give you only the settings that are concerned with opening new tabs so you don't have to scroll down 50 pages)
4) double-click browser.newtab.url.
5) In the dialog sheet "Enter string value", type the URL of your desired homepage. Then click OK.
6) Open a new tab to make sure it works.