With no reference to what it sounds like now, what you want it to sound like, or the setting (style of song) my answer is .. try compression first.

Like ROG said "It's very difficult to be precise without hearing the track or the mix which it's part of"

Others can give a lot better response if you give us something to work with.

No offense meant (honestly) but;
the original question is kind of like saying that you just drywalled a room and it came out pretty good, so what color should you paint it?

I have no idea without hearing (seeing) it.

Typical vocal chain -
EQ
Compression (similar to ROG's Limiter suggestion)
Reverb

not always in that order.




Make your sound your own!
.. I do not work here, but the benefits are still awesome