I haven't played with Fusion for years. It was originally provided as a bonus with Inventor Professional. If it is anything like big brother Inventor there should be constraints that can be applied to the parts. The first part in an assembly can be grounded - usually to the X_Y plane. Subsequent parts can be constrained to part #1 - or to each other, and then just one of them constrained to part #1.
That in a nutshell is exactly how SW works in bottom up mode.
Left Pic is an assembly just in a rollback mode for discussion. At this point the distributer body was imported & fixed to default XYZ origin. We need something to start but it can be any part in any orientation that makes sense. Now bring in another part, the bushing. Define its mates which in this case are concentric to the hole & co-planar to the distributor bottom surface. (ie nothing to do with assembly origin although that is possible too). With a button click on the bushing it shows me all the mates associated to this part, the 2 I just defined as well to any other parts or references as they accumulate. Then its just a matter of rinse & repeat. Bring each part in succession & mate it to whatever makes logical sense. It may relate to the initial part or a different part or a reference or a sub-assembly or whatever makes sense.
Right Pic shows a later stage, the parts with yellow shade are displayed on.
Left pic is snapshot of underlying files separated by type. You can see the assembly ^file above^. A Drawing document of this Assembly (Right pic example)
Below that all the individual Parts which are kind of the lowest level entity. Now they can be referenced or called into any other assembly or sub assembly but nothing changes at the part level. Any change made to a part automatically becomes refreshed & updated in an Assembly. And maybe this better illustrates why if I just rename 'bushing' to 'bushing1' (within Win explorer vs SW utility), the assembly cant know about that change & will complain, because its expecting 'bushing' and from this folder/path.
Now this is just the basic assembly workflow. There are all kinds of other capabilities that have specific purposes. I really should watch some Fusion videos for my own curiosity but I got the impression it was much the same, just different command words. And/or I assumed it was much like big brother Inventor.