The Legislative Lookup page is an external page you can choose to share with your supporters. The link for it can be found in the 'Useful Links' section of your dashboard:
Customizing the page that is launched by this link can be accomplished via a custom template. Please note that template customization is outside of the scope of Salsa Support, so this is something you would need to work on within your organization or with a 3rd-party/partner.
Custom web templates are discussed here. Each web template has its own template key. You can use 't/xxxx/' in the Legislative Lookup URL (shown above) where xxxx is the key of a template that adds CSS/JS to modify the layout.
Example of URL without template applied:
Example of URL with custom template '12345' applied:
After you've worked with your partner (or internally) to get that custom template set up and identified the URL which will then reference that custom template, you can then share your customized Legislative Lookup URL with the outside world!