Let's start with the basics.

You have your account. Either through work or the personal account you signed up for. Now make sure you have your information in correct.

Go to your Setup and edit your personal information in the "My Personal information" section. Make sure you have your name, address and phone number in correct.

Now go to the "Email" section and make sure you have the right email address (This should be done already) and create an email signature.

Something like:

Regards,
{!User.FirstName} {!User.LastName}
{!User.Phone}
{!User.Email}

[and you can add a logo or picture by using the html code for example]
img src="http://www.yourpicture.jpg

Obviously you can add a lot to your signature, this is just an example.