Default [Q] HELP!! (sideloading a rom)

Im trying to sideload magio rom rc6 on my htc one s. I start adb, i go to my computer and open cmd and then i ran the command "adb sideload" i kept on getting "error:closed". I tried it multiple times but i still got the same error. Now im getting a message that says "error: more than one device and emulator". What should i do. Please Help!

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What i did is before doing adb sideload i did adb usb. That fixed the error