1. Ensure the Ubuntu Universe and Multiverse repositories are available for use:

As root (e.g. using sudo), uncomment (remove the # marks from) the lines of your /etc/apt/sources.list file that include Universe and Multiverse
If your system does not contain entries for Universe and Multiverse, append " universe multiverse" to your main Ubuntu repository line
Alternatively, you may use graphical tools or other tutorials to enable the Universe and Multiverse repositories--the exact method of enabling is not important to the TDE installation process

2. Ensure the Ubuntu Recommended Updates repository is available for use:

As root (e.g. using sudo), uncomment (remove the # marks from) the lines of your /etc/apt/sources.list file that include -updates
If your system does not contain entries for -updates, copy your main Ubuntu repository line to the end of the /etc/apt/sources.list file and append -updates to the distribution name
Alternatively, you may use graphical tools or other tutorials to enable the Recommended Updates repository--the exact method of enabling is not important to the TDE installation process

3. Add these lines to your /etc/apt/sources.list file:

For Precise [Ubuntu 12.04] LTS (v3.5.13.1)

deb http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu precise main
deb-src http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu precise main
deb http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.13/ubuntu precise main
deb-src http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.13/ubuntu precise main

For Oneiric [Ubuntu 11.10] (v3.5.13.1)

deb http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu oneiric main
deb-src http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu oneiric main
deb http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.13/ubuntu oneiric main
deb-src http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.13/ubuntu oneiric main

For Natty [Ubuntu 11.04] (v3.5.13.1)

deb http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu natty main
deb-src http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu natty main
deb http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.13/ubuntu natty main
deb-src http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.13/ubuntu natty main

For Maverick [Ubuntu 10.10] (v3.5.13.1)

deb http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu maverick main
deb-src http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu maverick main
deb http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.13/ubuntu maverick main
deb-src http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.13/ubuntu maverick main

For Lucid [Ubuntu 10.04 LTS] (v3.5.13.1)

deb http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu lucid main
deb-src http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-v3.5.13/ubuntu lucid main
deb http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.13/ubuntu lucid main
deb-src http://ppa.quickbuild.pearsoncomputing.net/trinity/trinity-builddeps-v3.5.13/ubuntu lucid main

4. Add the GPG signing key:

sudo apt-key adv --keyserver keyserver.quickbuild.pearsoncomputing.net --recv-keys 2B8638D0

5. Install Trinity:

sudo apt-get update
sudo apt-get install kubuntu-default-settings-trinity kubuntu-desktop-trinity

Live CD Images for Ubuntu with Trinity preinstalled are available here

Common Problems:

1. kgtk-qt3-trinity can cause certain applications to crash. If you experience crashes try removing this package, but note that you will lose TDE open/save dialogs in all applications.