Creating a contact is the first step to organizing your texts! To do so, you'll want to select Contacts in the top left area of your screen. Then click "+".
This will then prompt you for your contact's information. Once entered, click Create. You can then find your contact in the contact list below and select it to send a message.
If you ever need to edit your contact's information, simply select the contact from the list to open a chat window. Then, select the Contact Info icon at the bottom of the chat window to open and edit!