There are a few different ways that you can add frames to your timeline in Photoshop. You can either use the frame tool, or you can use the layer mask tool.
If you want to use the frame tool, simply select it from the toolbar and then click and drag on the image to create a frame. You can adjust the size and shape of the frame by clicking and dragging on the handles. Once you have the frame the way you want it, you can add a layer mask by clicking on the “Add Layer Mask” button in the toolbar.
If you want to use the layer mask tool, simply select it from the toolbar and then click on the image to create a mask. You can adjust the size and shape of the mask by clicking and dragging on the handles. Once you have the mask the way you want it, you can add a frame by clicking on the “Add Frame” button in the toolbar.
Both of these methods will allow you to add frames to your timeline in Photoshop. Experiment with both methods to see which one works best for you.