Everyone has already mentioned great tips, find something that whets the whistle. Most large OSS projects now label a lot of their bugs with a 'beginner'/'get-started' tag. Start where your interests and that work collides, and work from there. If it doesn't float your boat, you learned something by trying, and find the next thing that intrigues you. Reddit is a better community now than SO, but SO does have a lot of answers. However, most large projects (epecially in JS) have gitter/slack/discord/irc/x groups that are either resolving issues, or answering questions, just be patient.
Another way I've been also told is helping with documentation on certain projects as well if bandwidth doesn't permit code dives.