Use the Mask tool to show a portion of a layer selectively. e.g., Create a circle mask over an image, then the image will only show the inside of the circle.
You can convert any Boolean group or layer to a mask by selecting the layer and clicking the "Use as mask" button in the top toolbar or selecting the layer, right-clicking, and tap "Use as mask".
Once a mask is created in the palette, if you don't want the next layers you place to be cut by that mask, you can separately group that mask and the layers you want to be clipped to restrict the usage scenarios of the mask.
To better use the mask tool and avoid the other layers being clipped by the mask, you can try a simpler operation as follows:
Select a shape and an image on the canvas simultaneously (hold [shift] and click to select multiple selections). After the selection, right-click and tap "Use as mask", then you can directly use the graph as a mask for the selected image.
(Mockitt will automatically group them and turn the graph layer into a mask.)
Note: The mask tool uses the filled alpha channel or shape to mask the above layer. However, since PNG files are stored as alpha channels, JPG format layers cannot be used as masks because it does not have alpha channels.