Basic chords on the keyboard are easy - but it's crazily beneficial to have a basic understanding of some really simple music theory to start with. To be able to work out a chord, rather than just being able to play ones you already know is incredibly useful.
Here's a crash course - assuming you can find the white notes already, i.e. you know where to find C, B, G, F, and you know that a sharp is the black note above the white note with the same name.
You need to understand tones and semitones first. A semitone is where you move from one note to the note right next door. For example, from C up to C# (the black note just to the right of C, before you get to D). Note, that if you start on E, and move a semitone up, there is no black note, so the note a semitone above E is actually the white note F.
A tone is simply two semitones added together. For example - G, through G# and onto A. The total distance, G to A is a tone. If we go back to the "no black key situation" of before, starting on E - 1 semitone moved us to F, a second semitone moves us to F# (the black note just above F). So E to F# is a tone, even though one note is white, and the other black. It's all to do with the "missing" black note in between E and F, and also in between B and C.
We'll now go for simple triad (three note) chords in root position (basic shape).
If you want a simple major chord, you need three notes:
-The root note (starting note - in a C chord, this is C, in a G chord, this is G etc etc.)
-The next note (called a THIRD) is two tones above the first note. So if we started on C, we move to D (one tone) and then to E (a second tone).
- The third note (called a FIFTH) is a tone and a half above the first. So, we were on E, a tone moves us to F# (see example above) and a semitone takes us to G.
So we have our 3 notes for a C Major chord - C, E and G.
Try following the steps and work some others out... For example, a D chord. Start on D for the first note, move two full tones for the next note (D, to E, then up to F# - missing black note!), then a tone and a half to the next note (F# up to G#, then the semitone up to A).
Any questions, do ask, it's quite hard to explain through text, and dead easy to explain with someone sat at a piano with me!