Installing fonts

Hi
I couldn't see an obvious place to post this so i hope this is the correct spot.

I am totally new to Macs and almost 2 weeks ago recieved my MBP
I have installed some fonts (some came in folders others didn't. I wanted to delete all the fonts from "downloads" to stop my computer being messy and slow (this can be done on a normal windows computer) and all of them deleted fine but i went to empty the trash but kept those that didn't come in a folder when i downloaded them saying "can not empty teas (such and such font) is in use" which i assume means because it's an installed font.

Is there a way to get these to go from the trash?

How did you install them, with FontBook?

Yep double clicked the names of them then that came up and i hit "install font"

If the fonts are still listed in FontBook then right click to remove them (there is no convenient remove button)

That won't remove the font from the system though will it?