Yes, you can change the Register Now text on header banner image. Please follow the steps below:
1) Please don’t forget to take a back up of the file prior to any changes.
2) Login to the admin dashboard.
3) Navigate Appearance -> editor menu.
4) Select Main Index Template (index.php) from the right side of the page listing.
5) Search for the following line:
<?php _e(‘REGISTER NOW’, ‘tyler’) ?>
6) Replace ‘REGISTER NOW’ with your text.
7) Update the file.