My Galaxy Tab 3 8" SM-T310 Storage Space running out

My Samsung Galaxy Tab 3 SM-T310 8" Tablet is telling me that my Storage Space is running out. I have inserted a 32 Gb Micto SD Card, but can not seem to store anything on it. Can someone please advise me why this is the case, please? I seem to recall reading somewhere, that Google has altered its Android Programme to inhibit people from storing things on SD Cards. Why therefore, do they provide provisions for an SD Card, or is that for Read only?? This seems to be a major step backwards in my opinion. Any information greatly appreciated. Thank you