Re: How do you make the gmail account your default mail?
Just to reinforce the point made by Feliciano, if you intend to use a Gmail account with an e-mail client that does not support 2-step authentication (which is a lot of them) you must do the following once you are logged in to your Google account for any service:
1. Go to https://myaccount.google.com/
2. Navigate to the "Signing in to Google" link and activate it.
3. Search for "2-Step Verification" link, which will read as being "On" by default. Activate it and follow the steps to turn it "Off." Part of this will require you to manually enter your existing password.
After you've turned 2-step verification off then any e-mail client should be able to access your Gmail account if you've provided the correct password. Many more modern ones like the Windows 10 Mail App will actually include a step when you're setting up the account where a Google window is presented where you specifically allow the app or application program access and Google registers this.
~ William James