Using apt to install 4Pane
Before you can use the 4Pane repository, you need to tell the apt setup that it exists. You do this by adding the appropriate url to apt's list of known repositories, /etc/apt/sources.list. You must be the superuser to do this, so either su to root (debian, PCLinuxOS), or prefix sudo to everything (or do sudo bash) (*buntu).
First you may wish to make a backup of your current settings:
cp /etc/apt/sources.list /etc/apt/sources.list.bak
Then either use your favourite text editor to add the appropriate line, or do (using debian buster as an example):
echo "deb http://www.4pane.co.uk/debian/ buster x11" >> /etc/apt/sources.list
The line to add is different for different distros/versions; choose the appropriate one:
Next tell apt about the 4Pane public key (remove the 'sudo' if you've already su'ed):
wget -O - http://www.4pane.co.uk/4Pane.asc | sudo apt-key add -or, rather faster to type:
apt-key adv --fetch-keys http://www.4pane.co.uk/4Pane.asc
You then need to do:
apt install 4pane
and 4Pane should be both downloaded and installed.
Alternatively, use an apt front-end such as synaptic to add the repository and do the install.