Make a backup with Titanium Backup, dl'd the v4.1 ROM (Blur or Blurless), place on root of your sd card (not in a folder), boot into CW, scroll to Backup and Restore and select backup, go back to main screen with the power button, wipe data and cache partition, mount system, select Install zip From SD Card, Choose zip, zip for Darkslide should be at the bottom (press volume up key), install, press power button until you're back on Reboot System Now.
First boot can take up to 5 minutes so be patient.
*Edit*: if you want to also install the v4.2 update, repeat above steps minus Titanium and the wipes.
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