The fire button in my tool bar is gone, why? It's only missing on ground missions. I'm new to this so if I sound stupid, oh well.

Press P... A dialouge will appear that will allow you to scroll down, find the item / skill in question and right-click-drag it into your powers-bar.

Hey, thanks a lot! This is the most amazing game I've ever played! Again, thank you. Where do you go for answers to simple questions like this for people who have never done this kind of thing? The manual isn't much help.

you've found the right place, most questions can be answered on the forums. You might also want to check STOwiki.

BTW, be sure to check the power screen periodically, occasionally you will gain new abilities, and as you do, you'll need to add them to your power bar to use them.