Hello Jordan,
To change the slider contents follow the steps given below

1. Go to Dashboard >> Sliders
2. Click on Add New/edit button.
3. Edit slider heading and contents.
5. Add slider button Text with its link.
6. Select the slider featured image.
7. Click on Publish/update Button.

You may use the theme documentation link given below to customize your site.
https://www.luzukdemo.com/docs/expert-plumber/

Thank You.