Changing Themes

Hi,

I currently am working with the TwentyFifteen theme and want to change to Delicious. However, whenever I switch over none of my posts are showing up, only the title and media associated with it but not the wording. Even when I tried to make a whole new post it wont show up. I do not know how to do coding and don’t know a whole lot except what I taught myself about WordPress. Can someone help me??