Split your visitors between 2 different versions of your landing page and measure which one performs better.
1. In Optimize, create a new experience and select A/B test.
2. Use your current landing page URL as the "A" page.
3. Create a Variant, and enter your test landing page URL for the "B" page.
4. Pick your conversion goal for what is a "win". Usually it is a form submission or button click.
5. Decide on how to split your traffic (50/50 for fast results, or 80/20 if you are worried about sending half of your traffic to an untested page).
6. Run the test and see the results start to come in!
Don't quit the experiment too soon. Wait for statistically signifiant results or you may end up with misleading conclusions and pick the wrong winner. The nice thing is that Google Optimize will tell you when you have enough data to make a decision on a winner.
Google support has more detailed instructions on how to use Optimize