how did george philip telemann use the german harpsichord?

Answer 1

With his fingers?!?

Answer 2

He sat in front of it, flexed his fingers and struck the keys. I know this is a frivolous answer, but, really, your question is so vaguely worded as to deserve little else. There is a classical music section, you know, on which this question might be better posted - with more explanation as to what you want to know.