How to use a bluetooth mouse on an Android Phone?

I have a RedMi Note 3 with CM13 installed. I bought a Phone bracket to watch videos on my bed. To interact with my Phone without the bother to lift my hand, I tried to use a bluetooth mouse. My Phone can connect to the bluetooth mouse, but shows no pointer and no reaction. I searched throw the Internet, but the results are all about how to use a phone as a virtual mouse to control a PC. I really don't know how to filter them out. Could you give me any guide on it? Thank you.