how do you change buscar to estar

I do not understand your question! Perhaps you mean the Present Progressive, which is a form of estar PLUS the gerund or -ndo form of buscar.

busco = I look, I DO look, I AM lookING
(the Present Indicative, that you learn first of all, has 3 English meanings.

estoy buscando = I AM lookING (the Present Progressive only has ONE English meaning, concentrating on "right now."

If this NOT what you need, please explain further, perhaps with an example.

Sra