Follow this link to get detailed instructions
Side-effects of using Free account (source: StackOverflow):
- No need for a paid account, but it's harder. We use free accounts for automation and they work. The problem is that the certificates for the "free" accounts expire every week, meaning that every week you have to recompile the WebDriverAgentRunner so the certificate is issued again. The configuration and automation is a bit more complicated, but it is certainly possible. The process is described at Real Devices Setup manual from Appium website.
- You can only automate specifically built simulator apps (app.zip) in a simulator and native apps (ipa) that are signed with a developer certificate. It is not possible to automate a production app signed with a release certificate.