Firstly under file, then new tab, and with regards to the addons, they are a matter of taste and use. browse the addons, extensions, plug ins, search engines and themes,have a quick read, then make your choice according to your needs and tastes.
Go to the recommended addons section, and browse, I personally recommend the Fasterfox extension, (which can quicken the loading of web pages),
https://addons.mozilla.org/en-US/firefox/addon/1269
and Adblock plus (which does exactly what it's called,) extension , https://addons.mozilla.org/en-US/firefox/addon/1865
and last but not least Plain Old Favorites, which will import all your favourites from internet explorer, so you can use them directly from Firefox
https://addons.mozilla.org/en-US/firefox/addon/668
You can also customise your Firefox with a choice of themes etc also
The options to customise your browsing experience are too many, to mention here, but basically you install what you like, then enable your choice in the tools section, above your address bar under addons . restart Firefox. You can always disable/uninstall chosen addons if your not happy with your choices.
Getting started with Firefox
http://en-gb.www.mozilla.com/en-GB/firefox/central/
Recommended Addons
https://addons.mozilla.org/en-US/firefox/recommended
Extensions
https://addons.mozilla.org/en-US/firefox/browse/type:1/cat:all
Themes
https://addons.mozilla.org/en-US/firefox/browse/type:2/cat:all
hope this helps