In order to install a hotfix from the GUI, you have to have an inactive partition already running the base version of the hotfix you are trying to install. For example, if you are currently booted on HD.1 and you want to install your hotfix (let's say it's 11.4.1 HF3), you'll have to have the base image of 11.4.1 installed on HD.2 or HD.3, and then you'll install your hotfix on top of that base.
Or you can do this through TMSH and I believe it'll install the base image, and then the hotfix on top of that in one step:
install sys software hotfix .iso volume