To set this up, first install the aptlinex package as root:
apt-get install aptlinex
Next, open Iceweasel and type about:config in the location bar. Click the I'll be careful, I promise! button and create the following four entries by right-clicking anywhere in the window:
These two should be created as New -> String values:
network.protocol-handler.app.apt and enter the value /usr/bin/gambas-apt.gambas
network.protocol-handler.app.apt+http and enter the value /usr/bin/gambas-apt.gambas
Here is how the entries above should look like:
The following two should be boolean values (can take either values of either true or false):
network.protocol-handler.warn-external.apt and enter the value true
network.protocol-handler.warn-external.apt+http and enter the value true
Here is how the two entries above should look like:
Next, you will need to click on a link which starts with apt:// and select the default application to open these links.
The first time you click on an apt:// link, you will be prompt with this window:
Choose the /usr/bin/gambas-apt.gambas application to open these links
Finally, provide the root password in order to start installing the DEB package
This is it.