How to put a diameter dimension on a 2d sketch

I have a small sketch and the instructions are to put a diameter dimension on it even though its a 2d sketch with just lines.The actual sketch lies within another sketch.I hope this makes sense to someone.I cant figure out how i put the sketch up on here.

Change the axis line to Construction (centerline) type. When placing the dimension click the centerline (not the endpoint of the center line) and the second point or line. Click on opposite side of the center line from second pick to place diameter dimension (if you pick the same side as second pick it will do radius instead of diameter). Zip and attach your file here if you can't figure it out and I'll create video using your file.

Thanks JD,

Every time I try and attach a file it gives me an error.I have tried .RAR and .ZIP with no luck.

How large is the zip file? Did you save with the feature tree in a rolled up state before zipping?

Here is a video.

Notice that depending on mouse position it either shows radial or diametral dimension.

(if you used Pro/E in the past - forget Pro/E method - wayyy too many clicks)

Now I understand,thanks JD.just one other thing is the diameter symbol not supposed to appear next to the dimension?

Now I understand,thanks JD.just one other thing is the diameter symbol not supposed to appear next to the dimension?

It will appear in the drawing.

In Autodesk Inventor it appears in the sketch - not sure if there is a way in SWx, but I never paid attention as it is pretty obvious even without the Ø symbol.

I suppose it would be obvious to a person who is used to 3d cad programs, I have only ever used auto cad in a mostly 2d environment so it wouldn't be as obvious to me. In the exercises I am following the symbol is present so my thinking was it will appear on the sketch area. Oh well you live and learn. Thanks for the help it is much appreciated.