Fluxx 4 updated to version 4.0.1
+ p455w0rd's Library
+ Wireless Crafting Terminal
^ Random Things to 4.1.10-Phanta
Type in the modpack name (Fluxx 4) or paste the following url into the search box.
Finally, click Install at the bottom right of the launcher after you select Fluxx 4 from the list on the left. The launcher will handle everything else!