If I understand correctly, this would use the same notes in different views? How would it make it clear or obvious which instrument the different view is for? The idea makes sense from a theoretical stance (to see the same notes in different views). I can try this. But yet I also like seeing the different instruments in the “Write” and “Print” views so it’s clear which is for which, and so that we could optionally get a duet or trio going.
All around though: thank you. Grateful for the time and help in this.
Thank you. I will try this.
Make sure you’re looking at the same layout in Print Mode. It’s not automatically the same layout you were seeing in Write or Engrave. Select the right one in the left column if necessary.
This is a small mistake virtually every beginning Dorico user will make at least once… But maybe you already discovered it.
Same pitches, different “notes” for each transposing instrument in the Sax family.
Feel free to ignore this 
and others have answered already, so you might be fine with where you are.
I think you have added a Soprano sax from the empty template. Click back to Setup mode and you should be able to add an alto sax. How? at the very bottom left of the Setup window, is a little icon (Single player) +, click that, search alto sax, Add.
In Write mode, make sure Edit menu > Transposed pitch is selected or see this post from Janus above.
Check your soprano notes are the same as on your music sheet. If not, ask here.
To transfer notes from soprano to alto,
Write mode - Full score, this tab is to the right of the modes along the top (if it does not say, Full score, it will be soprano sax or alto sax, change it to full score in the drop down menu).
Click on the first note of the soprano part then: Edit > Select to the end of flow.
Edit menu > Copy, then click then double-click just to the right of the time signature in the alto part, and Edit menu > Paste.
There are a few things that could go wrong here as we cannot see what you have input or any screenshots which will help us, but it might get you further. If not, and something messes up, do Edit, Undo … a few times.
If you get this far, or near it, then we can attend to your layout questions. In Print, in the left zone, should be the Full score, Soprano and Alto. Click through them so you see what has happened.
@arco has described the steps to add a second player and copy the notes.
Here’s an example score that shows my method of using one player with two layouts.
saxes.dorico (506.8 KB)
You’ll see in Setup mode that I’ve added a player with a soprano sax. In the right-hand panel, you’ll see a soprano sax layout, and also an alto sax layout. If you click on the alto layout, you’ll see that it’s wired up to the soprano player, meaning that it’s looking at the same notes.
In Write/Engrave/Print mode, there’s only a soprano sax, playing a written (transposed) C major scale, which is concert Bb. If you switch to the alto sax layout, you’ll see that it’s properly labeled Alto Sax (because I renamed the layout), and the alto is playing a written G major scale, the same (transposed) pitches as the soprano sax.
As I indicated above, I did this by adding a soprano sax to a new score, setting the key to Bb major (which looks like C to the soprano sax) and entering the scale. Then, in Setup mode, I right-clicked on the soprano layout and duplicated it.
Then I right-clicked on the new layout and renamed it to Alto Saxophone, and right clicked again to add a clef and transposition override.
If I change any note in the soprano part, the alto part automatically changes as well, and vice versa.