Cant install CWM recovery? topic

Hi i am trying to install clockworkmod recovery so that i can install cm11 rom. I download the cwm file and copy to sd card, then switch off phone and boot into recovery and install the file from sd card. Then phone goes into cwm recovery but if i reboot and then switch off phone and boot into recovery again it just goes to stock android recovery! Anyone knows whats happening and how to solve? Please help