When an icon is clicked, how do i make so it clones a tool into the players backpack/starterpack?

Instead of lumping your curiosity into one amorphous request, it'd be helpful to split apart the things which you are asking about and demonstrate how you have attempted to resolve the problem until now. It is much more fun for us, who sometimes enjoy writing answers, to see that you're putting some effort in as well.

Always start with the most useful ROBLOX Lua reference: the official wiki. Here you can search for pages that describe all of the objects and functionality that you're interested in.

Also, make sure you're familiar with the beginner scripting tutorials, such as this one and these ones.

Now, to point you in the right direction regarding your question:

Checkout the GUI ImageButton instance, and in particular the MouseButton1Click event.

Checkout the :Clone() method, which can be used on any object in a game.

All you need to do is :Connect() to the mouse event of the icon, use :Clone() on the tool which you want to copy, and then set the Parent field of the duplicated tool to the Player's backpack.