Version Update

I've just created a WP website using the Simple Catch theme 2.6.6. There's a notification to upgrade to 2.6.7 however it also warns about losing any customisation. I'm new to this and am obviously worried about just clicking the update button and losing everything that I've been working on. I'm also not that confident about creatng the child theme at the coding level. i sthere any easier way to deal with updates in the future? Yes, I'm also doing regular backups.