Hi @Naty Howard,
Welcome to the new Wix Blog!
To tweak the blog design:
1. Click the Blog page in your Editor.
2. Click Settings.
3. Click the Design tab to customise the relevant sections
Post page has its own customisation settings.
Please refer to these articles for more information on designing your blog (and how to access post page settings): https://support.wix.com/en/new-wix-blog/designing-the-new-wix-blog