How to get a token to work via API in the SendPulse service?

Question

API

Good time. I've never worked with an API before, so don't judge too harshly. I'm trying to get a token to work with the API in the SendPulse service. Authorization instructions are offered: https://sendpulse.com/ru/integrations/api#auth
As I understand it, a POST request can be sent through a regular html form, which I did by substituting the data that the system gave me in the account settings:

<form action="https://api.sendpulse.com/oauth/access_token">
        <input type="hidden" name="grant_type" value="client_credentials">
        <input type="hidden" name="client_id" value="02d5XXXXXXXXXXXXXX2f8359">
        <input type="hidden" name="client_secret" value="7879a3XXXXXXXXXXXXXa198fe">
        <button>Отправить</button>
 </form>

After submitting the form, a page like this opens:

https://api.sendpulse.com/oauth/access_token?grant_type=client_credentials&client_id=02dxxxxxxxxxxxxxxx2f8359&client_secret=78xxxxxxxxxxxxxxxxx98fe

I can't figure out where the access_token comes from? and what does Authorization: Bearer have to do with it?
I would be grateful for any comments on the topic! )