How do I access these 3 hidden volumes?
A typical APFS volume under Catalina will have 5 partitions.

Macintosh HD: the read-only volume that stores the OS
Macintosh HD - Data: the 'normal' everyday volume where you save stuff to.
Preboot: a small amount of data used ... before booting.
Recovery: the Recovery volume that you boot to when holding Command R
VM: caches for virtual memory.

These are all essential, and you should not need to access them or do anything else with them.