I’d like to know how can I convert an already finished desktop project to android platform. I am aware that this kind of question was already posted (From Desktop to Mobile - Mobile - Epic Developer Community Forums), but there were no actual guidelines as how to do it.
So there are going to be a couple of things you are going to need to do in order to get your PC game ready for a mobile platform. Firstly, the materials and textures will need to be simplified and reduced in size if they are complex. You will then need to optimize your project to be targeted for Mobile Hardware and set up a device profile.
The best advice I can give you is to provide our documentation on Mobile Game Development. Let it be said that porting a game that you have developed for the PC platform to the Mobile platform is not going to be an easy task. On the opposite spectrum, porting a game to PC from Mobile is going to be much easier.
Mobile Game Development
The largest issue with Mobile development are the limitations that are introduce when going from the PC platform. What I would do is open a copy of your current PC project, and change the target platform to Mobile/Tablet. Then begin the process of optimization and removing features that mobile platforms simply cannot support (i.e. tessellation and distance fields).