Given a portfolio $P$ with return $R$ and market-beta $\beta$, we have
$$E (R - R_f) = \beta (E R_M - R_f)$$
Now, what does leveraging $P$ have to do with $\beta$? How it is affected if we leverage the portfolio up or down?
For example, say I want a portfolio of beta 1. Then I divide through by $\beta$ to get $$E(R - R_f)/\beta$$
... but what exactly is this? How do I obtain a portfolio using leverage that gives a beta of one?