hdmedia h8 storage problem

[robflo1970]

i recently bought this unit because it looked ok, mainly for the price and storage,
this unit comes with 2gb ram and 16gb,
the problem is this, everytime i download and app it goes to the 2gb and i can't change the location, also it i want to download a movie it desnt give me the option to swicth the storage. it keeps saying NO ENOUGH SPACE, even it happens with apps,  which it means that i can only use a few apps mavy   or max 10. the main reason that i bought this unit was because it said 16 gb space to save,
all i want is for this unit to star using the 16 gb instead of the 2 gb because it fills up really fast.

can someone please help me with this.

the unit that i bought was this

HiMedia H8 Octa Core Android 5.1 4K Smart TV Box 3D Bluetooth Media