Fieldsets are cool. They group a bunch of fields together. You can control a whole block at once too!
1. Go to Marketing Activities.
2. Select your form and click Edit Form.
3. Click the + sign and select Fieldset.
4. Select the fieldset and enter a Label.
5. Drag the fields you want into the fieldset.
6. Here's what it should look like when done.
There you have it!
You can dynamically hide/show the entire fieldset depending on another field. Learn about visibility rules.