Aspect ratio

I have a client that wishes to have the file done in 1080x1920. What’s the best way to do this?

When you create a new project select “HDTV” for the Camera Size.
This will make the project 1920x1080

It needs to be 1080x1920. Is that an option?

If you mean 1080x1920 as a tall project instead of wide, then no.
However you could make a custom resolution by clicking the “+” icon
nest to the “Camera Size” field and making a custom resolution by
typing in the values in the Width and Height boxes. Just remember to
it a unique name that is not already used.