I've no experience with VR13 but it should function like any other A2SD-enabled ROM. Assuming you have already flashed VR13 to your handset and it's working:
1. Mount as removeable drive and copy contents of the memory card to your PC.
2. Power off and replace existing card with your new one.
3. Boot into recovery.
4. Choose the option to partition the memory card. Create an EXT2 partition for A2SD (512MB should be ample) and a FAT32 partition for storage (the remainder of the capacity). Set SWAP to 0 (if offered the choice) as it's not advised.
5. Still in recovery, mount the sdcard ("MS-USB toggle" in Amon_RA, in the "Advanced" menu in ClockworkMod) and copy the contents you previously backed up to PC (step 1) back onto the memory card.
6. Unmount the card and reboot. This may take some minutes to complete fully depending on how many apps you have installed, as they will be moved during initialisation.
7. Check your available internal memory; it should now have noticeably increased.