Where is the submit button in a WeChat Official Account app?

I am trying to follow the WeChat Official Account tutorial to build an app.

In the step of

1.4 Basic Configuration for Developers

4. After the restart is successful (python main.py 80), click the Submit button. If the prompt "token verification failed" appears, check the code or network link. If the token is successfully verified, you will be redirected back to the Basic Configuration page. Click Start.

However, based on the tutorial, there is no submit button related code. I cannot find the submit button.

When I open the pages through WeChat Official Account in the app WeChat, it just shows "hello, this is handle view".

Any guide? Thanks

main.py

import web
from handle import Handle

urls = (
    '/wx', 'Handle',
)

if __name__ == '__main__':
    app = web.application(urls, globals())
    app.run()

handle.py

import hashlib
import web

class Handle(object):
    def GET(self):
        try:
            data = web.input()
            if len(data) == 0:
                return "hello, this is handle view"
            signature = data.signature
            timestamp = data.timestamp
            nonce = data.nonce
            echostr = data.echostr
            token = "xxxx" #Enter the value in **Basic Configuration ** at Official Accounts Platform.

            list = [token, timestamp, nonce]
            list.sort()
            sha1 = hashlib.sha1()
            map(sha1.update, list)
            hashcode = sha1.hexdigest()
            print "handle/GET func: hashcode, signature: ", hashcode, signature
            if hashcode == signature:
                return echostr
            else:
                return ""
        except Exception, Argument:
            return Argument

I figured out the submit button here in the tutorial is referring the submit button at

https://mp.weixin.qq.com/

开发 -> 基本配置 -> 服务器配置 -> 修改配置 -> URL

After you fill the URL, that submit (提交) button.

(Unfortunately, the WeChat Official Accounts settings panel only has Mandarin language not like the developer doc. But hopefully my screenshot will help locate it.)