KeePass is an open source password manager that is hosted on your own computer. This has the advantage of not trusting your data to a third party service. The disadvantage being the lack of connected access between devices. Below you will find a guide on how to setup KeePass for use on your desktop device:
After downloading and installing KeePass, you will need to create a new database by selecting New Entry.
You will be prompted to enter a Master Key which will be used to secure this database of passwords.
Once the database is created, you will need to add 2 entries to the data base to store your login credentials, one for your login password and one for your mailbox password.
After you have opened the login page URL by selecting Open URL, ensure you have the browser selected as your last click before returning to KeePass. Once back at KeePass, select Perform Auto-Type. This will automatically enter the Username and Password and enter it, moving you along to the Decryption page.
The mailbox password requires a slightly different approach than the login password when using KeePass. Since the Mailbox password does not contain a username, you can not use the Perform Auto-Type feature found in KeePass. Instead, you will make an entry with just your mailbox password. When you have gotten to the Decrypt Mailbox page on ProtonMail:
Select your mailbox password entry in KeePass. Select “Copy Password” in the menu bar. Once this is selected you will have 12 seconds to paste the password into the password field on the Decrypt Mailbox Page. After 12 seconds, the password will automatically be deleted from your devices clipboard to prevent it from being compromised.