Looks like it doesn't support HiveSigner. You can use the Hive Keychain browser extension if you're on a laptop or desktop. If you're on mobile your best bet is to use your posting key.
If you don't have it handy, your posting key can be found in the PeakD "keys & permissions" page, or wallet.hive.blog.
So I'm just trying to do the keys & perms thing.. about the master password: is that the password I entered in HiveSigner?
yea, that should be the one. Be careful with master password, it can be used to change the other keys. Use posting key (lowest access) wherever you can.