Metamask is basically the app you use to run Ethereum programs you can get it from the chrome or firefox store works for a bunch of things like minds etc. Basically runs Dapps like what steemit is going towards.

The issue may be that you need to link and create an account then it should work without issue, you can claim the referral after the account is made tested it out.

(I did check is it down though and the site seems to be working http://www.isitdownrightnow.com/dmunity.com.html)