To install the full App suite on a mobile device, you firstly have to download what3words app from the App or Play store. This contains the offline map and 3 word directory.
Then, you need to download ‘App Sheet’, again from the App/play Store. It has a paper plane is the icon. It will, when downloaded, it may try to get you to sign in. Ignore that and close it.
Then download the Mull app to run on the phone. Open this link in your Smart Phone.