The process of backing up your website will depend on how and where it is hosted. The process can be summarised as being possible via one of two or three likely methods:
The exact process will vary depending on the web interface that you have been given by your ISP so specifics cannot be given here. However cPanel, Plesk and many other well-known web based control interfaces all contain backup options. Search your control panel for an icon titled 'backup' or 'full backup'.
The exact process would vary depending on the services and access you have to your web server. You may be able to undertake these tasks fairly painlessly. Firstly by going into a file manager type utility provided in the control panel interface provided by your ISP. From here you would create a zip file of your entire website root folder.
You may also have access to an interface from where the website database/s are managed and this will likely have an option to create backups/exports.
Once backed up you would then ideally copy the zip file and database export off the server to local computer's storage for safe keeping.
If you are running your website on a platform that uses droplets or kubernetes or is a manually installed VPS (virtual private server) with no web admin interface then the only option you will likely have for managing your server is via a CLI (command line interface).
The exact process would vary depending on the web server type that your website is run on and for that reason, if you have such hosting you probably already know how to undertake this relatively simple administrative task.
However as a rough guide, you could backup your public website root by running the following command from within the root of your web space:
zip -r website-export.zip public_html
And your database (assuming it's MySQL/Maria DB) could likely be extracted using a command such as:
mysql -u UserName -pPassWord DatabaseName > export.sql