Popular twitter client MetroTwit has now been made available for Windows 8 RP. Its available in Windows 8 Store.
To install this, Open Windows 8 Store and if MetroTwit not shown in New apps, just search by choosing ‘Store’ and it’ll be listed.
Click on it to open its Install page and click on Install
It’ll start the Install process & you can see at top right the message of Installing… and then Installed message.
And you can run it from its tile on the StartScreen
Its still a Preview, so might find some glitches. You can send reviews, feedback from the Windows 8 Store.