Well, you can't have an Arduino make radio waves at 433 MHz, no matter what, so you need to add a radio module. I found the RFM22B radios on EBay, I think they're about $3.00 apiece, they have up to 100 mw. output (with carefully chosen antennas, of course).
The SPI hardware interface requires pins 11, 12, 13, an interrupt (pin 2 or pin 3) and a chip select pin. The library for these is on Github under the title of RadioHead. It is just about the best documented library I've ever run across.
I like these little buggers so much that I designed a Nano plus RFM22B board, so that if I want 433 MHz, I start with that board as my base. I've got four nodes up and running in a ten node network, and all they ever do is work right.
What I would warn you against is the Moteino line of boards. They have an electrical flaw which can put 5 v. on your 3.3 power rail, and for some reason, it seems to be impossible to get them to work with the usual use of timers in a program. I blew $100 + on some of Felix's boards, and threw them all away as unusable except in toy applications.