What problem are you having "doing something" with the model?
Can you attach the file here or provide the Grab CAD link?
I can select "high light" individual features but then can do nothing with them. I can draw a "new" sketch over the top of the feature and get dimensions that way. Was hoping to use the model for machining purposes and avoid re-creating the wheel if you know what I mean.
Without seeing your model or what you downloaded we are all just guessing....
Post the link to the GrabCAD file you downloaded.
Post your model you have modified here on the forum. Use the Advanced Editor link in the upper right of the dialog box.
That way we can see what you are working with and offer suggestions.
Did you use Defeature or FeatureWorks?
If you are using CAM enabled machines, why do you need dimensioned feature sketches?
If you need a 2D drawing, you can add dimensions in the drawing views.
If you need to modify the part, you could use the Direct Editing & other functions for most/many changes.
As J.Mather & Anna have requested, post the model, and be specific about how you want to edit the part. You may be pleasantly surprised at what can be accomplished on "dumb" models.