Hi!
In order to create Google Recaptcha field follow next instruction:
1. Open Membership plugin.
2. Move to Registration Fields section of Profile tab.
3. Click Add Field – https://prnt.sc/ek6c27
4. Choose Google reCaptcha for field type – https://prntscr.com/ek6cpq
5. Add Google ReCaptcha Site Key and Google ReCaptcha Secret Key.
6. Tick Enable, Required and Registration to make field required for registration.
7. Customize other settings.
8. Click Add Field.
9. Click Save fields for Registration Fields tab – https://prntscr.com/ek6evd