Right-click, shift-click, or do whatever you need to do to save the XML file(s) above to your computer. Then do the following.

Firefox users:

Visit about:support and click "Profile Directory" to get the path of the profile folder.
In your OS, go to that folder.
Put the XML file(s) in an HTTPSEverywhereUserRules subfolder (create it if necessary).
Restart Firefox.

Chrome users:

In your OS, go to the folder where the HTTPS Everywhere extension was installed. On Windows, that's %USERPROFILE%\AppData\Local\Google\Chrome\User Data\Default\Extensions\gcbommkclmclpchllfjekcdonpmejbdp\VERSION (replace VERSION, of course).
Put the XML file(s) in the rules subfolder.
Edit rules.js and add the new file(s) to the list, like this: var rule_list = ["rules/default.rulesets","rules/skew.org.xml",];
Restart Chrome.
Reinstall every time the extension is updated (which Chrome won't notify you of...you just have to notice that the ruleset stopped working.)