main menu modifying

how do i modify the main menu items and link them to vm catagory that i have created....
i am using the hot ecommerce template,and did instaled it using hotstart inst.

Easiest way is to copy whole link from your browser when you are in that category and put that in menu item, you also need to change menu item type to simple link so you could just enter link in text.

how do i change the shop menu in the hot template...

You alter regular joomla menu, but you have new menu item type "virtuemart" when you have vm installed. So is you want to reference some product, product category of something from VM you set menu item type to "virtuemart" then you get special options for that menu item.