Following my post about setting up your model's shadows for date/time-stamping and export, I had assumed the first steps to be self-evident - but for the avoidance of doubt...
Your model needs to be Geo-located to show correct shadows - because the UTC Time-Zone and its actual location are both important.
Use the Model Info section for this.
For example, the shadows at 08.00 in Southern England and in Northern Scotland are quite different despite them sharing a Time-Zone.
Also the model's default 'North' is the Y Green axis, but there might be an offset shown orange in the results. Make sure the Z Blue axis is 'up'.
If you have modeled the building 'on axis' but have a building that is in reality 'off axis', you can resolve this by making a group of everything, and then rotating that group to suit the actual North, when you edit that group its axes with it will still align as before; any further modeling within that group will also remain 'on axis' for your building, whilst it is actually placed in the world correctly.
The model's Shadow settings should now reflect its Geo-location.
Alternatively of older versions, if you want to adjust the 'north solar axis' manually, then there's a su_ tool available in the EWH - https://extensions.sketchup.com/extension/393f5153-ba5f-4f5f-849f-46b32cf64bd4/solar-north
I have Geo-location set up on my usual Template for my regional location, set manually using the Model Info dialog's section.
You can set up templates for various locations if you work in several different areas.