Using 2D Sketch to draw at different angles on a part

[jcasey7460]

Instead of spending another 1-2 hours on something that is probably fairly basic I decided to ask here...

I am trying to take a drawing that was started off on an XY plane, and turn it 90 degrees to an YZ plane (I think) and then sketch the next part of the drawing. I attached a some images (one of the drawing exercise and another one that shows you what I am trying to do (support-fixture-dim-sides is the title)and also a moving gif that shows the side without a grid), just to give you a better idea. 

How do I get the side (the rounded part) of this part so that when I draw a line it will draw from one of the sides. I am unable to Create New Sketch on either of those rounded parts, if I could that would solve it. So I figured something like projected geometry might work but nothing so far. I've been on this for a while so I need to ask someone.

Drawing included if it helps...

[JDMather · Accepted solution]

Use symmetry about the Origin.

Your Sketch1 is not placed at a logical location.

Your Sketch1 is missing at least one dimension.

[jcasey7460]

Thanks for the comment (drawing/sketches too). It's starting to make more sense now. I didn't get anything done yesterday but I learned something.