I Keep Getting This Error Message

Hi, first you need to select the part you want to sample. To do this, hold down the ALT key on your keyboard and then click the mouse to take the desired sample. Once this is done, apply the sample you have just taken to the desired point.

You have Healing Brush Tool selected in your tools panel.

For Healing Brush to work, you need to sample the area you want to sample from first and you do it by holding Alt key on the keyboard and clicking once to take a sample. Then, you move the cursor and click to apply the sampling point.

Rather like the Clone Stamp Tool, you option click on the area of the image you want to copy and trasfer to another part of it.

https://helpx.adobe.com/photoshop/key-concepts/clone.html

https://www.youtube.com/watch?v=c8Vo0_uEdUo