The two palettes you need are Layers and History. Go to the “Window” menu on top and click on those two palettes and they will show up on your workspace.
It is important to always be aware of what layer you are on in a PhotoShop image. When you add type, it automatically creates a new layer. If you paste another image into this one, it automatically creates a new layer. If you become frustrated because nothing you’re doing is working, it’s probably because you’re not on the right layer.
If you open your image and the layer labeled “Background” is locked, it means you can’t make any changes to this layer. Just click on the lock icon next to the word “Background” and it will become a normal layer.