By default the first track that will pop up in your program will be the first track listed in the global view located at the bottom of your window.
If you decided to open a full score, most of the time this track will be a vocal track displaying standard notation only.
To access the tablature related to your guitar track, simply select a guitar track from your global view.
Please note that you can enable the "multitrack" feature from the "view" pane and display all the included tracks on the same page.
You also have the possibility to choose which track you want to display once this multitrack mode activated.