Hi,

Is there an easy way to make my image to be completely green?

Thank you

I suggest stepping through the Tutorials in Inkscape's Help menu. They are easy and will answer many of these basic questions.

You did a rectangle and two ellipses.

Ellipses have a green fill, rectangle a green stroke. 

To turn a fill to green, if you use the color palette bottom of screen, select the objec then, just click on the color you want. If you want to set stroke color, shift-click or click with mousewheel.