negation only applies to propositions.
(p v q) is a proposition, call it r, so read ~(p v q) as "it is not the case that the proposition r is true".
p and q are also propositions, so e.g. ~p is the proposition "it is not the case that p".
Read [(~p) v (~q)] as "it is the case that either (it is not the case that p) or (it is not the case that q).
~(p v q) is thus true only if both p and q are false.
[(~p) v (~q)] is true only if at least one of p, q is false.
there is no "if" involved in either case.
postscript ok, I used "if" in a confusing way. to quote myself:
"~(p v q) is thus true only if both p and q are false." I used "if" here. my bad. there is really no getting around this circularity, but it's a circularity of informal English, not logic.
a better quasi-formal reading would be something like "~(p v q) is true" just means "it is not the case that [(it is the case that p is true) OR (it is the case that q is true)]".
in other words, even though we use "if" informally to explain these things, their meanings do not involve "if" -there is no contingency there.
Addendum if you need to convey these ideas in speech you can use pauses, as @Not_Here suggests, but to be really clear you need to name your conjunctions and disjunctions, e.g. "the disjunction of A and B is true".