When new versions of the themes installed on your blog have been uploaded to the Dotaddict resource center, the page has an additional tab named Theme Updates, which lists the themes with the installed version number and the version number of the update.
Then just use the action button Update.
If several updates are available, an action button at the bottom of the page allows to Update all themes at once.
Please note: any changes you might have made to the theme files will be lost when updating the theme.
The list of installed themes appears in this tab. You can select a theme by clicking on it and pressing Use this one.
The currently selected theme can be modified using the Edit theme files button. If the selected theme includes a theme editor, it can be easily personalized using the Configure theme button.
You can also deactivate a theme (for instance if you have compatibilities issues with it). A Deactivated themes tab will appear containing the list of these.
This tab allows you to browse the DotAddict themes repository either by alphabetical order, either by searching using the dedicated field. The themes that are already installed do not appear in the list.
If the theme you want to install (or upgrade) is not in the DotAddict repository, you can install it either by uploading it from your hard drive, either by entering its installation URL. A theme is always packaged as a zip file.