I want to turn my keyboard into a piano. So far I have manage to work out that I need to use [keyup and keydown] to activates those keys. What do I need to do next??????

When you say piano, you mean it should sound like a real piano, or just some synthesizer triggering notes with the keyboard? I'm not sure that [keydown] is good, cause it starts banging shortly after you press a key and doesn't necessarily waits for the key to be released. You can use [key] and have some steady envelope for your notes.
Anyway, after [key], [keydown] or whatever you use you have to send some value to an oscillator. You can do that by connecting [key] to [select] (check help patches) or [mtof] (but with [mtof] you're quite likely to get rather high pitches).
Simulating a piano sound is rather difficult though, you'll need to do quite some research for that.

I mean it should sound like a real piano (so for example if I press the a on the keyboard) that would be the middle C. would I have to record it and insert it or try and sample single notes on the keyboard?????

Thank you Alexandros for trying to help btw.

Elie... If you are looking for convincingly real piano sounds you might have your work cut out for you. The typical methods of emulating a piano would be to use FM synthesis (synth sounding), Physical Modelling (convincing but difficult to achieve) or to use multi-samples. The easiest route might be to use multiple piano samples loaded into various tables and then use tablay~ to play them.

Search for Floss Pure Data as it has very good simple guides on using arrays and tables.
Second look for free piano multi-samples such as http://bedroomproducersblog.com/2010/07/01/free-sample-shootout-3-acoustic-electric-and-toy-pianos/