Reduce the size of the logo on the Website

How do I reduce the size of the logo as it is on this website:
Unfortunately the theme does not allow me to customize from the WP Dashboard

Welcome to our community!

If you have a question about a specific challenge as it relates to your written code for that challenge and need some help, click the Ask for Help button located on the challenge (it looks like a question mark). This button only appears if you have tried to submit an answer at least three times.

The Ask for Help button will create a new topic with all code you have written and include a link to the challenge also. You will still be able to ask any questions in the post before submitting it to the forum.

Thank you.