To access CWM, hold the volume up button, hold the power button and then let it go, but keep holding the volume up button. Your DX50 will soon boot into CWM, after which you select "install zip from sdcard" (assuming that you placed stock_recovery.zip into the DX50's internal storage) and then select "choose zip from sdcard". You will now be able to see the zip files in your internal storage. Select stock_recovery.zip and reboot the DX50 from the CWM menu once it has finished installing. Boot into the stock firmware and select update system (assuming that you have already placed the update.img for FW 1.5.0 into the DX50's internal storage. And you're good to go!
Edited by bluesyfluesy - 6/27/14 at 9:21am