Manual instalation of SSL

Hi team,
im following this tutorial
https://help.optimizepress.com/article/1971-setup-free-ssl-with-lets-encrypt?_ga=2.94255773.1292037680.1540451571-937936461.1540451571
first of all when i install and activate the plugin i miss the option for auto-generate the certificate.
then i click on register account, after that it prompts me to:
Connection Information

To perform the requested action, WordPress needs to access your web server. Please enter your FTP credentials to proceed. If you do not remember your credentials, you should contact your web host.

it want my ftp login info. Is it normal? it should be already able to go to my directory when it was able to install plugin in a first place?

Or somebody just want my page info?
thanks for any info.