Use less of it?
Check the Linker Script (.ld) file, see what RAM regions are defined, and what you're putting in each. There's quite a lot of RAM but it's not contiguous, as it resides at different addresses within the address space.
If you initialize more than one RAM region, you'll need to manage those in the script and the startup.s file.
Make the RAM bigger in the .ld so you can get closure, and then look at the .MAP file to understand what is sucking up all the resources. Avoid large global allocations. Put frame/display buffers elsewhere.
