Pokemon GO: How to Join a Public Raid
There are essentially two types of groups that you can form in Raid battles: Public and Private. Private battles are password protected, so only those who have received the invite and code can join that group. The public group system will create a group of random players from all the Trainers who have joined the battle. You can either join these battles remotely or in person.
How to Join Public Raid Remotely
The first thing you need for this style of Raid is Remote Raid Pass. This pass has to be purchased from the item shop. And you can collect as many passes as you like unless you fill your item bag with it. Tap on the Main Menu, and hit the Shop button. Scroll and choose the Remote Raid pass. Ask someone who is at that Raid Arena to send the Raid invite. They can tap the “Invite Friends” option from the lobby and choose you for sending an invite. Now go to the Map view and enter the Nearby option. Select the Raid tab. You will see the invite, tap on it to join the battle. When you reach the lobby, choose the “Battle” option. Then select your Pokemons and wait for it to start.
How to Join Public Raid in-person
Open your app and go to the Nearby window. Choose the “Raid” tab, scroll through the available Raids and Tap on the one you wish to join. Once you are at the location, tap the “Battle” button. Select your Pokemons and wait for the match to start.
This is how you can join Public Raid in Pokemon GO. Looking for more Raid guides, check out how to join Private Raid and how to get Raid Pass.