The first way is to use the in-app updater. Click on the 'Update' link and then click 'Update'. bliss will update itself... you shouldn't even need to restart bliss.
The second way, in case the in-app updater does not work, is to simply download the new version and install it as before.
When updating bliss your existing settings and any fixes you have purchased will be retained.
In-app update is a new feature in bliss and there have been some teething problems. If, after updating, you find bliss won't start any more, please read the FAQ on fixing update problems.
Any other FAQs I forgot or clarifications required? Post your ideas below!