Account details such as username, email and password can be changed from the Settings → Profile tab → Edit Profile section.
Click Edit profile and your profile page will open in your default browser.
In order to change your email or password, click Edit account, change the desired details and press Save Changes.
Password can also be changed with the forgot password feature.
It is also possible to delete your profile here, but please be careful with this button: it is not possible to revert any changes after you confirm the deletion.
If you want to change your username, add your First and Last name and/or upload your profile picture, click Edit Profile.
Don't forget to press Save changes when you are done.
There are two other ways to change your profile picture: click on Change profile picture option or click on your profile picture on the dashboard main page.
Then just drag and drop or browse for the photo you want to use and press Upload Picture.
If you haven't done that already, you can also use the dashboard to connect your account to Facebook. Just Press Connect To Facebook and voilà!