When the Fed buys assets (government bonds, Fannies, etc.) from a bank, the bank gets back 'bank reserves', which are just a number in the bank's Federal Reserve account somewhere.
Those reserves can't be lent out. The bank can make no change to its lending, because it's a one-to-one swap (highly liquid government treasury -> bank reserve). A bank's constraint against lending more is its equity reserve ratio, which is unchanged by Fed asset purchases.
Again, this is not printing money; functionally speaking, US Treasuries are already 'money' to a bank (they are extremely liquid, widely traded internationally, safe, and in many contexts actually preferable to cash), so swapping a US Treasury with cash is just turning one type of money into another; no net creation.
There's a simple reason the Fed doesn't clear up this confusion: the central bank prefers people to think they are printing money, because credibility is important to their effectiveness. And the Fed doesn't actually print money, because they don't have the legal authority to do so. This is why Powell is regularly getting in front of Congress to urge more stimulus spending: he knows it's the only way to get dollars directly into the hands of ordinary Americans.