Problem in Hacking Android Phone

hi i am stucked at this point in hacking my android phone by using a reverse meterpreter payload..

i am using msfvenom to generate an apk file..

i have signed the app manually as stated here at the end.

http://developer.android.com/tools/publishing/app-signing.html

but when i transfer the apk file into my android and run it ,it throws error as

"

an existing package by the same name with a conflicting signature is already installed"

i am tired of this error. pls help..