The chrome or firefox browser (select via SETTINGS tab) will be used to create accounts. You will need to manually fill in the captchas
If you uncheck Browser signup, you will create accounts using HTTP requests (sockets). This is faster and more accurate, however you will probably be shown a captcha which to solve, you must have 2captcha credit (they are the only company offering to solve this type of captcha with requests)HTTP REQUEST SIGNUP
You can signup and purchase credit with 2captcha here
enter your 2captcha API key to the SETTINGS tab in the captcha box and you should be good to go.