1) purchase a new power supply. use a power supply calculator to see how much wattage your system requires, and then get a supply that is as big or bigger than what is suggested. DO NOT get a power supply smaller than what is suggested. DO NOT get a power supply that is more than 100W larger than suggested (unless you are planning on some major upgrades in the near future).
-Never trust a power supply that was plugged in when parts have been fried, simply throw it out (or better yet recycle it), and buy a new one that has a good reputation.
2) After you get the new power supply there is no guarantee that the rest of the hardware is working. You can hook it all up and pray that it works, but if it does not then you will need a 2nd computer that you can swap parts with in order to test your equipment.
-Keep in mind that you want to test 1 part at a time
-Some parts like Ram and HDDs need testing which can take several hours before problems show up
-Some damaged parts (specifically motherboards and power supplies) can damage other parts, so tread carefully