Hi Marian!
The best way to update is to use the WAF Setup tool.
Note that the actual release build will become available tomorrow (April 30th) before lunch.
We're currently working on the update script to make it as painless as possible. Since it's such a big update, there might some minor work to get the site running after performing the update. That's why we recommend that you do an update on a test version of your site first, so you can see what, if any, work must be done to make it work.
NB! Before you upgrade, make sure the server has .Net 4.5.1 installed.
Vidar