Literally just go outside and write ACAB on something. Dumpster dive something. Slack off at work. Map your neighborhood's security cameras. Delete your Instagram. Write a political prisoner. Start a garden. Drop acid. Give a homeless lady some hand-warmers. Put "out of service" signs on parking meters. Pick one and do it right now.
These aren't revolutionary acts, these are the calisthenics you do so you'll be in shape for the revolution.
You absolutely should also join an org or at least work on long term projects with other people. These are exercises to get you to think of yourself as an actor rather than consumer, not a replacement for organizing.