Typically, I will remove the Y coming out of the wall---then install the two P-traps and the tail piece on the strainer basket---
If there is a garbage disposer---loosen it enough to turn it,if needed---
I will then aim the P-traps at the drain opening ---figure out what combination of T- ---Street 45s or 9os that will give a nice neat installation.
In our area, dish washer drain can not be installed into the garbage disposer---so I have the entrance in the tail piece.
The vacuum breaker Joe showed is not required here--just a high loop in the dish washer drain line---just under the bottom of the counter top----
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