You can resize the artboard by selecting it (either clicking on the artboard title or double clicking on the artboard), then resizing it. However, if I understand correctly, you want your vector assets to resize as you resize the artboard, right? That's a completely different question.
I think your best bet is to group your icon on the artboard. You can then rescale them however you want to by resizing the group. You'll probably still hit some issues with the borders being the wrong size if you scale that way, so you may need to adjust them afterward.
Here's an example of how I resized:
Hope that helps!
Thanks for the reply appreciate, that make sense. I had discovered that but wanted to make sure that was the best way of doing it. Thanks for your help.
No problem! Good luck, and let us know if you have any other questions.