I live in West Virginia. I filed my regular taxes online, but now I have to mail my form 8379. I need an address. Please help

Send it to the same office you would send your tax return to if you filed using paper. For WV that's

Department of the Treasury
Internal Revenue Service
Kansas City, MO 64999-0002

See:
Where to File Tax Returns - Addresses for Individual Taxpayers By State, U.S. Possession or Foreign Country