Help downloading questcraft

When I try to download quest craft I get an error that says A task failed. Check the tasks screen for more info. QuestCraft | Now only v51 and above!: /data/local/tmp/_stream.apk could not be installed [INSTALL_FAILED_UPDATE_INCOMPATIBLE: Package com.qoxr.qcxr signatures do not match previously installed version; ignoring!]. How can I fix this?