You can download tor browser here.
https://www.torproject.org/download/
Tor sends your internet traffic through 3 relays a layer of encryption “peeled off” at each relay. If you want to hide tor usage or in Iran/China you must use tor pluggable transports. There is no tor for iOS (iPhone OS) apps claiming to be tor are scams.
Spread tor to as many people as possible and ideally donate.
If you can run a tor (non exit recommended from home) here is the guide
https://community.torproject.org/relay/
As to exit relays: “ The exit relay is the final relay in a Tor circuit, the one that sends traffic out to its destination. The services Tor clients are connecting to (website, chat service, email provider, etc) will see the IP address of the exit relay instead of the real IP address of the Tor user.
Exit relays have the greatest legal exposure and liability of all the relays. For example, if a user downloads copyrighted material while using your exit relay, you, the operator may receive a DMCA notice. Any abuse complaints about the exit will go directly to you (via your hosting provider, depending on the WHOIS records). Generally, most complaints can be handled pretty easily through template letters.
Because of the legal exposure that comes with running an exit relay, you should not run a Tor exit relay from your home. Ideal exit relay operators are affiliated with some institution, like a relay association, a university, a library, a hackerspace or a privacy related organization. An institution can not only provide greater bandwidth for the exit, but is better positioned to handle abuse complaints or the rare law enforcement inquiry.”
Also if you can’t run a full relay install this (none tor browser) browser extension to run a “snowflake proxy”
https://snowflake.torproject.org/
If you need it look into ultra private/secure operating systems that use tor like qubes (with whonix) and tails:
https://doc.qubes-os.org/en/latest/introduction/intro.html
https://tails.net/