Typically you have large areas of dual-ported memory visible to both cores, and HSEM provides a Hardware Semaphore method of signalling/interrupting between the cores.
How to do multi-core/multi-thread programming and the concepts are perhaps beyond the scope of the forum. I'd suggest reviewing some college level texts on the subject area, and then look at how you can apply that to your use case/application, and with FreeRTOS running independently on both cores.
Having multiple things actually happening at once can be a challenge for some coders used to more linear flow, and there can be some complex interactions which will be next to impossible to debug with single-step / breakpoint methods in real-time/interdependent systems.
I don't believe FreeRTOS provides a method to dispatch tasks on different cores, but there may be OS that do. The Flash code space is also shared.
Watch for cache coherency and non-atomic memory access.
