Learn Polish: Musimy odkryć to, co ma dla nas znaczenie. - We must discover what has meaning for us.

When English uses "what" to mean "the thing that" in the middle of a sentence, Polish uses the pair to, co (literally "that, which"). The to acts as a placeholder for the unknown thing we need to discover, and co introduces the description of it. Additionally, Polish grammar strictly requires a comma before co here to separate the two clauses, even though English doesn't use a pause.

Why use the perfective verb odkryć instead of the imperfective odkrywać?

We use the perfective odkryć because the focus is on successfully completing the action (making the discovery once and for all). Using the imperfective odkrywać would focus on the ongoing process, changing the meaning to "We must be discovering..."

Is ma dla nas znaczenie a common phrase?

Yes! Mieć znaczenie literally translates to "to have meaning," but it is the standard Polish way to say that something "matters" or "is important." You could very naturally translate this sentence as "We must discover what matters to us."

Why does znaczenie look like it's in the basic dictionary form if it's the object of a verb?

It is actually in the accusative case because it is the direct object of the verb ma (has). However, znaczenie is a neuter noun. In Polish, the accusative form of any neuter noun is always exactly the same as its nominative (dictionary) form.