Encoding/Decrypting a string of characters

You're given a string of characters told its a password and asked what the password, is how do you go about solving it?

For reference the sting in question is; HRoYW4gZ2FyYmxlZCBub25zZW5zZS4gVGhlIGNvcnJlY3QgYW5zd2VyIHRvIFEzIG9uIHRoZSBhcHBsaWNhdGlvbiBmb3JtIGlzICJCYW5hbmFzISI=