You can change your account password on your Airtable account page. To get to your account page, click the circular face icon in the top right of the home screen. This will bring up a dropdown menu with several options; select the Account option (which has a little silhouette of a head next to it).
This will bring you to the overview section of your account page. You can also go directly to https://airtable.com/account.
To change the password associated with your account, click the Update password option below your profile picture.
This will bring up a dialog where you can enter your current password and your desired new password.
If you signed up for Airtable with a Google login, you won't see the Update password option—you'll instead see a + Add password option.
Clicking this will send a password creation link to your associated Gmail account. You'll need to create an Airtable-specific password if you originally signed up with a Google login but would like to change the email address for your account.