Like any skill, singing takes practice. It also helps to get skilled advice. Lessons can't hurt (it it does not apply to what you are doing, you just quit). Lessons can be very helpful (in that they can help you to understand how the instrument works).

I actually find singing harder to master. There are no frets to get your intonation right, you just have to learn how to hear that sound in your head. Then you work to make that sound with your voice, then you work to develop vocal chops that make a great vocalist. It is the same as learning to play guitar except there are no stops to help you hit any note. No piano keys, no frets, and nothing to really look at. It is all internal, invisiable, and thus harder to master. When you play an instrument you first learn the mechanics and from that, you develop your sound (ie. you learn to play chords and scales and then you produce a sound). When you learn to sing it is the opposite and quite a be more complicated (you have to conceptulize what your sound is, then you have to learn how to make those sounds reliably). I find voice much more complicated to master.

Some people have just made a habit of singing or they have deep natural tallent (Jagger ect). Those are the exception... not the rule. Most people have to work to develop and then to maintain a trained voice (don't forget that the Jaggers of the world also have 50 plus years of practice). That is a BIG deal.

If you want to sing, and you can arrange to have lessons, I would recomend you try them. Even just beginner training could be very helpful as you start to grow your skill set.