On this page of the Disco Elysium guide, you will learn how to get a Prybar and how to use it.
The prybar is an extremely useful tool that will enable your character to open locked rooms, containers, and chests that you may encounter while exploring the world of Disco Elysium. Inside, you can find useful healing items, clothing, and money.
You can get the prybar at the start of the game. Exit the hotel and approach Kim's car.
Look inside, then open the Toolbox - you will find a prybar. Just select the dialogue option highlighted in the image above, and the item will go into your inventory.
When you have the prybar in your equipment and are near a chest or container, you will notice that the white outline has turned blue.
During some conversations, like the dialogue between Harrier and Kim near the locked container at the back of the hotel, you may see a dialogue option that will allow you to use the prybar. However, this requires a certain amount of physical points, meaning that you can fail the skill check to open it by force.