Dynamo for Revit is an open source project and free.
Download the install from:
Updates occur frequently so check regularly for updates.
Once install point Dynamo to the folder where nodes and packages live.
Start Dynamo, Settings menu, Manage Nodes and Package Paths...
Add the path where office Dynamo nodes and packages live...
PACKAGES
You may also wan to install some of the packages available.
Packages are libraries of nodes. They are generally free.
Go to the Dynamo packages web site to find the best to install:
https://www.dynamopackages.com/
In Dynamo under Packages tab Search for a Package, then select the ones you want to install.