Phone [Q] How can i use Internal Storage?

I am really in trouble!
I've just bought Samsung Galaxy S4 Korean made. In the storage option there are two general tabs:-
1- is about Sd card storage which is only 17.8 MB and
2- is about Internal Storage 16GB. So my question is that how can i use internal storage of 16GB as SD card data.
Another problem with my device is that whenever i wanted to put ext sd card (microsd card) it does not show any thing like preparing sd card nothing....
Please Solve my this problem i shall be very thankful to you!