Take this from the Alexander: adest, adest fax obuoluta sanguine atque incendio: multos annos latuit, ciues, ferte opem et restinguite.
Wherefore, he adsistere docenti, operanti has never at any time failed benedicere, periclitanti opem to be with his beloved spouse, ferre nullo unquam tempore to assist her in her teaching, destitit.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "opem" in a variety of sentences. We hope that you will now be able to make sentences using this word.