When I first started singing with my band it was because the singer had quit and we still had gigs booked so I had to get tolerable very quickly.
1)Find your range
Everybody has a range of notes they can hit. Elvis Presley had a wide range, Jim Morrison had a narrow range but both were good, strong singers because they sang song within their range. One fun and easy way to find it is to take a simple song and sing it in each key. some of them will be easier to sing in. Find the ones that are the most comfortable and then sing the scale for that key. This will help you get an idea of what songs you can and can't sing
2)Be kind to your troat
If you know you have to sing drink room temperature water instead of beer, pop, coffee ect. If you smoke you should probably cut back or switch to lights. Don't over do it. When you troat (vocal chords) get tired, let them rest. They will get stronger in time.
"Nobody paints by ear so why would I play guitar by sight?"