Installing procedure is, in my opinion, difficult for beginners. First you need to know how to use Linux (in this case Ubuntu). Next, you have to unlock and root your Nexus 4. Finally MultiROM Manager and Ubuntu Touch are installed. So you'd better be familiar with Nexus flashing techniques in order to succeed.
It's way too hard for me to write about every single detail that happened during installation. In case you are still interested, please follow this external link. Read the instructions carefully and take the steps needed to make your Nexus 4 dual boot two operating systems.
Installation going on!
Touchable dual boot menu shows up when powering up!
Ubuntu Touch up and running!