The issue is that the EyeCandy package is stored in the new Lazarus format of xml files - the author should have checked the box "Maximize compatibility of LPK files" in the package options to avoid this.
Nevertheless, you can fix the format of the lpk file yourself: Download the "fixlp" tool from
https://sourceforge.net/p/lazarus-ccr/svn/HEAD/tree/applications/fixlp/ (use the "Download snapshot" button) and compile it. Copy the binary into the EC_Controls folder of your EC_Controls installation and execute
fixlp eccontrols.lpkNow you should be able to compile the package. Start the IDE, go to "Package" > "Open Package File (.lpk)" and open the eccontrols.lpk file. Click on "Compile" to compile the package - it should work now. Then click on "Use" > "Install" and allow the IDE to rebuild itself. After a while the IDE restarts and you have the EyeCandy Controls on the component palette.
--------------------
[EDIT]
Or, to avoid having to patch the lpk file, I am attaching an already-patched version of eccontrols.lpk. Simply extract the file from the attached zip and write it over the orginal file in your installation. Then proceed with "Package" > "Open Package file".