If there is an elevator in a small high-rise building, you can take the elevator to transport the solar components to the top floor, transport them to the roof through the overpass, and then install them. Low-rise buildings allow construction workers to use a suspension to lift all components up to the roof.
Some upper floors have a small door that can lead directly to the roof, which is more convenient and can be transported directly for installation.
The water tank is a large part. If the opening is small, it will be inconvenient if you can't get in. The only way is to use ropes to hang it from the ground floor. The build team is responsible for the specific method, so don't worry too much.