Install recording software onto the computer. The computer is the hub of a home recording studio. A good computer for home recording will have a lot of RAM memory (at least a gigabyte or more) and a large hard drive. Cakewalk Sonar and Apple Logic are two popular choices for recording software that are available to purchase. Audacity isn't as robust and versatile as the others, but it is free to download and is a good choice to begin learning on.
Connect the sound card or audio interface to the computer. Sound cards that normally come with a computer aren't good enough. Plug the sound card into a free PCI slot. If the computer doesn't have a free PCI slot available, use an external sound card. Choose one that connects through a Firewire connection for the best results.
Connect the microphone and keyboard to the audio interface using stereo sound cables. Check the female connection that plugs directly into the audio interface. If the tip of the connection has a black circle running around it, then it is a stereo connection. If it has no circle, it is mono. Mono connections can be used, but stereo connections often give better sound. Make sure the microphone and keyboard are plugged into the "input" jacks on the audio interface.
Plug headphones into the "output" jack on the audio interface. Start the computer and run the recording software. Set the input and output devices to the new sound card. If the software can't find the audio interface, make sure all of the hardware's drivers are up-to-date. The studio is now ready to record.