There are templates available on-line...and I seem to recall I've even seen an application where you up-load the jpeg of your floorplan and apply the template (rotating it to get the facing correct)
But the Moderators do not permit links here.
It is really just a matter of over-laying a compass (with all 360 degrees shown) over the exact center of your floor plan (again rotated to get the facing exactly correct). Then you can see how each sector really falls and compares to the rooms. You still need to extrapolate then how the qi flows.
To really understand Flying Stars, though, this chart is only the beginning.
You need to consider the chart for this Period and its effects
You need to consider which are the auspicious sectors and which the bad ones (which is independent of the flying stars and tells you how the stars will behave in each sector) and more.
This is why so many people talk about Flying Stars, but so few benefit from it