If You're a newbie, then my suggestion is to try a good multiband compressor. It will do the best for You, as You're not familiwar with advanced compression settings. That will make possible to use a superfast attack times for de-essing range of compression while maintaining natural timbre of vocals with soft compression ratios and times.
If You'd like not to disturb the voice entirely, use as narrow de-essing range as possible, as cutting wide can be heard.
Then don't forget to place EQ (if necessary – miltiband compresson is actutally a form of dynamic EQ-ing) after, NOT BEFORE miltiband compressor.
And use a good (nylon, not metal) pop-up filter for recording vocals. This may sometimes prevent from extensive "essing".
PS. If You or Your singer records in front of a wall or glass or any sound-reflecting-something, it may bring "essy" effest to the track. Plain surface (especially glass) can reflect high frequencies quite significantly and bring them back to the mic with additional delay.
PS. II. What kind of a microphone You use? I mean is it a proper condenser one, reaching 20 kHz? If the answer is YES than that's OK. Despite common opinions, mics that aren't good in high frequencies may emphasize essy range by cutting high end - it's a bit complicated to explain, but happens. Lack of hi-end harmonics means more freedom for essy frequencies in the middle to expand –*to achieve a clean, crystal sound that puts vocals in front of a mix, You'll probably need EQ-ing the vocal line, and that may ampliffy what You're trying to avoid.
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