Google Reader (http://google.com/reader) and TinyTinyRSS (http://tt-rss.org/redmine/) are online news aggregators. To use these services you need an online user account. With such an account you can read your subscriptions
Liferea as a desktop aggregator cannot provide the global accessibility that a online news aggregator provides. While you can access an online aggregator from virtually everywhere, Liferea needs to be installed and configured on every PC you use. Also it ensures no direct synchronisation between the different installations.
Using an online aggregator you can workaround this situation. You can subscribe to your online account from all your Liferea installations and will have synchronous feed lists and item states everywhere. At the same time you can still use a web browser to log in to the online aggregator directly if you are at a public terminal for example.
Shortly after subscribing the feed list of your online account should appear and items should be retrieved.
Liferea 1.8.12 and later supports TinyTinyRSS versions starting with version 1.5.3.