I don't know how you're "supposed" to restart from there but you can always hold the power button down for ~5 seconds until the machine does a hard power-off and then turn it back on again.
Press and hold the power button until your MBAir shuts off (should take about 5 seconds)
Now, press and release the power button once, then press and hold Command-R.
You can release the keys when you see the Apple icon followed by the progress wheel or bar. That will boot to your Recovery system.
And - open terminal from the Utilities menu, type resetpassword hit return and follow prompts
If you upgraded to Yosemite, you can go to your App Store, then download the Yosemite installer.
QUIT the Installer, instead of continuing with a reinstall. Use one of the several methods to make an Installable USB flash drive for the Yosemite installer. Google for those methods - one that I like is the DiskmakerX app, which will do the job very neatly.