Boosting default attack with support gems

Hello everybody, big noob here, just played since open beta started so pardon the stupidiy of my question if that's the case :)

So, can i boost my default attack with a support gem ? For example: Fork, can i use Fork on my default attack or must i only use it to boost another skill .. like Poison arrow for example.

Thanks in advance !

Support gems can only buff up other gems, so no you cannot buff up your main attack.