Importing back ups into Acronis.

Hi, i have Acronis installed on my C:\ drive, and my USB drive's (X:\) incremental backups are going to a second (G:\) internal SATA drive.

If i need to reinstall my Operating System (and therefore the Acronis program as well), how can i 'import' my incremental backups into the new Acronis installtion, so that i wont need to create a brand new backup of my USB drive, and just carry on making incremental back ups like i was before the OS re install?

Thanks for your help.