The best way to work with components is to follow Fusion 360's R.U.L.E #1: Before doing anything, create a component and make sure it's activated.
All objects created after activating the component such as sketches, bodies, construction geometry, joint origins, etc. are created in that component.
This has several advantages:
- On activation the timeline is filtered to show only those items in the timeline that pertain to that component. That will make the quickly growing timeline much easier to work with.
- If a component is exported to the data panel with "save as" this will also export the complete parametric design history.
- Drawings can only be created from components
- The joints in the "Assemble menu only work with components.
When another component needs to be edited for example to add geometry, it should be activated before doing so.
You already have a sketch and a body that are not part of a component, but as the design is simple there is a remedy.
Right-click on the root of the browser and select "Create component. That component is automatically activated.
Then drag the sketch into that component and the body is also moved to that component. This most only works in simple designs.
To copy a component and create an instance, right-click on the component in the browser and select copy.
If you want that copy to always be the same as the original component, right-click or the root of the browser and select "paste. This creates an instance of the component.
If you want to create a copy of the original component that can be edited independently from the original, select "paste new" instead.