Interfacing with SD card in Graphics Display Designer (MicroChip)
I'm assuming you are using Microchip Graphics Library? If so, there are plenty of examples given to help you do this. I haven't used the library with an SD card, but it shouldn't be much different to displaying a image from program memory.   



There is a tool (Graphics Resource Converter) to create the C code from an image to a const array in memory designed to work with the library. If you are just starting with all this, you may want to try using this and loading from program memory first, then from the SD card. Post the relevant bit of your code if you have problems.

Read the help documentation, particularly about the Graphics Object Layer, Graphics Primitive Layer, and the bits about PutImage and External Memory.