Help Newbie needs help htc desire and imac

[jms1977]

Hi members hopefully you can asisst me , heres the problem i cant seem to find my sd card on my desire when connected to imac? i am trying to install apk files, live wallpapers etc ive tried my sd card in a card reader but it says something like unable to read this disk thanks for any advice im sure il be back for more lol!