how to connect to an external monitor

http://www.apple.com/shop/product/HFQL2VC/A/moshi-mini-displayport-to-hdmi-adapt er-4k?fnode=f5b35208fb55fb412a2da05c616a25917c575a472c9003a928e6a8618618c4d55351 132add544481f42a1fef2b735d2c48dd09af34451d75a387bb5d0a4e64f48e91aa43434f692f2a27 755967f98b30952587d156b4e7bfa999c2b47b0214ac

Apple carries them, plugs into Thunderbolt port. Under "Arrangement" of dual displays in Preferences->Displays, uncheck "Mirror" to have different images on each screen

BestBuy and others carry similar products which work as well as the ones Apple sells.