There are a couple of considerations when "micing" your instruments. Personally, I don't record anything except my voice with my microphone.  Remember, the mic picks up everything in the room including room harmonics. This may be ok depending on what the individual is looking for. Part of the fun for me is to try and make a recording as close to commercial as possible. I don't have a "proper room" for recording. I use my home office. It aint ideal.

If I do record acoustic guitar, which is rarely, I plug directly into my pc via an audio interface. The signal is direct and clean, no sound dynamics from the room. See below for more on this.

Here is my setup, not exactly my same equipment but it will give you and idea as to what you will need.

Microphone

Audio Technica. My model has been replaced with an upgraded AT2035. 

Boom Stand for your mic. If you are recording your guitar with the mic this will allow for easy placement. If you are going to sing, it will allow you to stand which is much better than sitting. If you are going to sing, getting rid of room harmonics is another topic.

Audio Interface

You will need an audio interface to connect to your pc. I use a Scarlett Solo. Its low cost very small and simple to use. Your guitar - in the case of acoustic you will need a pickup for the guitar if it does not have one already will plug into the interface. If you use a mic to record your guitar, it will plug into the interface. I looked up your keyboard, looks like it has a built in interface so you should be able to plug directly into your pc via USB and have your DAW recognize it. See below...

DAW - Digital Audio Workstation

A DAW is a piece of software installed on your pc which will capture the signal coming into the pc via your audio interface. Be it voice or guitar. I will outline the 3 that I have and why I have them and how I use them. It will also accept mp3 files that you may want to add to your music. Just import these directly from your pc. 

Audacity - completely free and there are countless video tutorials on YouTube on how to use it. This is an incredibly powerful DAW at no cost what-so-ever. I used to use this a lot but moved on - see below

Reaper - this is not free but not expensive either. Lots of video tutorials on YouTube and Reaper is an easy way to add drums via free VST files. See YouTube for this.

Amplitube - Not free - you will have to check pricing. For what I do, I use Amplitube most of the time. Amplitube is actually not a DAW  as in the case of Audacity or Reaper - but it contains a very useful DAW within the software. Amplitube is an amp modeling program that is too complex to go over here. But it is worth the price of admission for what it contains. Worth checking out on YouTube. 

Hope this helps. Writing your own stuff is great fun. Best of luck with it.

Edit, I just saw Christopher was typing at the same time as myself. He is THE GUY to go to with any questions on guitar.