e signature verification error when I try to install a ROM

[Benny444]

Ok, so I've never installed a custom rom before. I rooted my newly acquired S2 (I9100M - wife's castoff :-\ ). I installed ROM manager and backed up everything. I then downloaded a custom rom onto my SD card and tried installing it through ROM manager. That's when it tells me I have e-signature verification error....installation aborted. I've tried different roms and installing it through different programs and manually. It just gives me the e signature error every time. Unfortunately there is no way, at least as far as I can tell, to toggle that verification off on the S2. I'm just at a loss as to what to do. Also, please speak to me as if I am a child because I feel like I'm in over my head. Please help!