When you press Q you open the Tools box at the upper right.
With the mouse wheel you switch between theese tools.
You can also assign a Key for this in the Control Options.
You have to copy the AddOns into your Add-Ons folder in the Blockland Installation Folder.
You have to activate the AddOns.
Start a Game, klick on the Add-Ons button in the "Start a Game" Dialog and check the checkboxes of the AddOns you want to activate.
For a few addons you can assign keys in the control options, they have to be activated so you can see them in the control options.