Go on to the download page. Accept EULA, that is the End User Licence Agreement, download, install and start to use.Upgrade to version 3.1
As usual before install - like when you modified your data - create a safety bachup by clicking on "Settings", "Database...", and click on button "Safety backup.
Before installing the new version remove the old one. From Windows' "Apps and features" panel click on remove myCollection. Do not worry, your database will not be deleted, and can be used after the new version is installed. The new version uses another database, so collections must be imported first.