What I like doing -- if you don't need any past transaction history -- is just delete your Beam Wallet (make sure you have your twelve word passphrase or you'll never see your Beam again). Now, you also need to delete the directory because I think the Beam uninstall leaves them alone.

An odd thing I noticed the first time I attempted this was that after entering my passphrase to restore my coins, the sync process still didn't sync. I didn't see the estimated time remaining. If this happens you need to again uninstall the wallet and delete the directory again (Beam Wallet). For some reason I discovered the third try was a charm: perhaps some initial files hang around awhile. Oh, actually I created a fresh wallet with new passphrase...then immediately uninstalled it and deleted the Beam Wallet directory. Finally at this point I downloaded the Beam Windows wallet a final time and restored with the passphrase and my coins synced in 10 minutes.

Important: As I said, be certain you have the correct twelve word passphrase before attempting this.