To access them, you'll need to partially or completely disassemble parts of the engine. This is not a DIY job for someone without significant mechanical experience. It requires specialized tools and knowledge of engine disassembly and reassembly. Incorrectly removing or replacing freeze plugs can cause serious engine damage.
Instead of trying to locate them yourself, if you suspect a freeze plug issue (like a leak), it's best to consult a qualified mechanic. They have the expertise and tools to safely diagnose and repair the problem.