Header questions

Hi, I want to increase the size of the logo without having to use the parent functions.php. I have created a child theme. Would I place a functions.php file in the child theme and add the following code? Or do I need to do something else to make this work? // The height and width of your custom header used for site logo. // Add a filter to catchbox_header_image_width and catchbox_header_image_height to change these values. define( 'HEADER_IMAGE_WIDTH', apply_filters( 'catchbox_header_image_width', 600 ) ); define( 'HEADER_IMAGE_HEIGHT', apply_filters( 'catchbox_header_image_height', 167 ) ); One more thing, I wanted to add a couple of graphics to the side of the logo that are linked to another site or page, is it possible to do this with the free catchbox theme? Thanks for any and all info you can provide. Corinne