STEP 1
You have to create a script first, I'll guide you though a simple script to turn on a light, to do this:
Goto Settings - Automations & Scenes - Scripts (from the tabs menu on the page)
1. Press the "+ ADD SCRIPT" button on the bottom right of the page.
2. Select "Create new Script"
3. Name your script eg: "Turn_on_Cinema_Light" No spaces and give it a icon if you like.
4. Press "+ ADD ACTION" from the drop down select "Call a service"
5. From the Service drop down select "Light: Turn on" and select "Choose device" and select your light you want to turn on. you can also select brightness and color if you like.
6. Press Save
7. To test the script, from the Traces menu (right top side with 3 dots), select run script, the light should turn on.