unable to select edges/sketches

I'm an sketchup user and since I kept hitting the limitations of sketchup I'm trying to switch to Solid Edge.
However while drawing I get the feeling I'm doing something wrong. If I follow along the tutorial everything works fine but as soon as I'm trying my own work I'm unable to select edges/sketches.
An example:
I created a box, in this box I would like to have a cutout for a rubber ring (seal).
So I created my 1st sketch with the outline of the cutout path in the top pane of the box.
the 2nd sketch has the outline of the cutout itselve.
However if I'm trying to relate the top of my cutout (2nd sketch) to the top of my box/origin no point's can be found.
Can you help me with this?
Thanks in advance,
by the way: I'm creating an ordered part