Hi Ian,
You will need to use custom CSS classes to make the tabs look a certain way.
This can be written in the Appearance tab of your tab container widget:
For eg please refer:
https://freefrontend.com/css-breadcrumbs/
https://freefrontend.com/tailwind-tabs/
Additionally, there are also inbuilt Mendix wizard steps with styling that can be reused/repurposed for your requirement. You can find them in the toolbox--> building blocks as below: