Vectorportal is very good resource for beginners who are just learning Adobe Illustrator. In order to modify Vectorportal files you will have to prepare them for editing with commands like Ungroup, Expand Appearance, Unlock All etc. Most of these commands are located in Object Menu. Here are few advices on potential problems with editing of Vectorportal files:
1. Can't move image? Maybe the object or part of the object is locked. Go to Object > Unlock All. Or maybe the layer is locked. Check out Layers palette and unlock locked layers.
2. I want to modify left wing, but I can only select left and right wing together. Go to Object > Ungroup to ungroup objects.
3. Use Object > Expand to expand gradients, fills, strokes and gradient meshes...
4. Use Object > Show All to show hidden objects.