The check mark is there so you can select something to do with the ‘gear’ button. For example, if you wanted to delete both passwords stored in your vault, you press the two check marks and the press the gear button to choose the delete option.
When you installed the browser extension in your browser and have logged into it (you need to login to the extension separately from the web vault), you should be able to login into website by going to the login page, and either
press the extension icon and press the name to auto fill the details.
use the keyboard shortcut (Ctril + Shift + L for Windows, Cmd + Shift + L for Mac)
right click on the login with your mouse and select Bitwarden, Auto-fill and the website in question.
That pin button is a browser thing that allows you to pin important extensions so they stay visible. In your case, you still have plenty of real estate for extension icons but some people with dozens of extensions have to pick and choose which ones stay visible in the browser and which ones you have to hit a drop-down to find.
Edit: Bitwarden, being a password manager you would want quick access to, is one extension that you would probably want to pin so that it is always visible.
All software has the odd item of not intuitive user-experience. No software is perfect.
For example, on an old Mac (and probably on current ones, I have not used one for some years), the “easy to use” computer, if you drag a disc drive symbol to the waste paper basket then obviously that will delete the files on that drive. That is the obvious thing that action will do. However, it doesn’t do that.
An equally not intuitive example is on older Windows, where the obvious way to turn the contraption off is to press a big button marked “Start”? Really?
I recommend you press that pin and allow it to always be visible in your browser.
After this, you will be able to see the icon at all times, so if you navigate to a webpage with a saved login, the icon will change to display a number, indicating the number of login/passwords are saved to the extension.
When you press the icon, you will then see the auto fill information saved. Press the name to autofill the username and password. Or if you wish to copy the information yourself, you can press the person icon for username, and the key icon for password.
