If someone can't sing, is there an easy way to learn how to sing like online or something for free?

no i dont think so maybe you wold have better luck doing somthing else singing is a gift people are born with

If you want to learn to sing try going to your local instrument retailer and see if they host voice lessons there or if the know a place where you can have voice lessons. I don't think you can learn to sing online unless you have like a video conference with a voice teacher. You can also try to look for lessons in some of the community centers they are great and for a reduced price.

uhh...go to a school and ask teacher advice about singing

It kind of depends... Are you just not well practiced? Or are you tone deaf...? There isnt really a cure for tone deafness, so you're kinda lost if thats the case. But if not, then you just need to practice. Start with easy songs in your voice range, and once you're able to sing those well, pick stuff out of your range to try and improve it. There are plenty of places online that will teach breathing and practice techniques...you could also try joining a choir. That would help a ton!

a tape recorder and practice practice practice.... Part of being able to sing well is being able to hear, I mean really hear music.... when the notes are high or low and how long to hold them. listen to a favorite song, listen to when they sing higher and lower and try to do it yourself... record it, play it back and listen to how you did. singers practice by playing the notes on a piano most of the time and then copying the notes with their voice.

Anyone can learn to sign reasonably well.

if you have no natural talent you're never gonna be amazing.. but you could learn to stay on key at least. If i was you i'd try to find something you're naturally good at and excel