"Inclure" (to include) and "exclure" (to exclude) are what are called antonyms, i.e. opposite words. "Inclure" (to include) means to add, while to "exclure" (to exclude) means to remove.
However, these two verbs are from the third group, both end in -ure and share almost the same endings. For here, the difficulty comes from the past participle. Whereas including makes its past participle by "inclus", "exclu" loses the "s" and only makes it excluded.
J'ai inclus les fraises.
J'ai exclu les pommes.
The easiest way to remember it is to put it in a feminine form: "elle est incluse" but "elle est exclue".