To install:
npm install ender-wallet -g
Easy. If you're using an npm < 1.0, you can leave off the -g.
To run:
cd into a directory with an ender build, then run...
ender-wallet open
Then hit localhost 8083 (in webkit||firefox) and you'll see what inside's your ender wallet.
To convince you to try it, here's a screenshot:
Since Ender is purty young and this project is even younger, both are liable to change alot, and probably ender-wallet will break alot. So make sure your Ender is as fresh as possible.