First of all, I wanna thank you guys for creating Construct 2. I'm really having a great time creating games.
But back on topic.
The title says it all. The camera for my platform game is really small, you can barely see anything, so is there anyways to increase the size of it?
You don't increase the camera size. You have to increase the "Window Size". A larger window will show more of the layout, and doing so will make the objects appear smaller. The reverse is also true, a smaller window will show less of the layout, and make the objects appear larger.