In SPR it's under install menu right above the actual installation selection. It says allow update.zip. The file would need to be named update.zip in this case. update.zip not Update.zip
Hook is right, there is no "allow" option in CW, in this case you do not need to rename to update.zip. In CW you would select install .zip file from sd card and then select .zip, then you can scroll and select the file to install.