Hello Carlos,
There are 3 areas in the product documentation that will help us to answer this question:
hco Command - Check-out
https://docops.ca.com/ca-harvest-scm/13-0/en/command-reference/get-started-with-ca-harvest-scm-commands/hco-command-check-out
Defie a User-Defined Process
https://docops.ca.com/ca-harvest-scm/13-0/en/administrating/define-lifecycle-processes#DefineLifecycleProcesses-DefineaUser-DefinedProcess
Use the System Variables
https://docops.ca.com/ca-harvest-scm/13-0/en/administrating/use-the-system-variables
What you will do is go into the properties of your Promote process and set up a post-linked UDP process that performs a Check out - Reserve Only command. This will place "R" tags on the items in the package after they have been promoted to the next state. In order to provide the correct details to the hco command you are going to use the Harvest "System Variables". These will allow you to "pass in" the broker name, project name, state and package name, etc.
Here is an example hco command that might accomplish what you are wanting to do:
hco -b [broker] -en [project] -st [state] -vp "\MyRepositoryName" -p ["package"] -ro -usr [userid] -pw [password] -s "*.*" -to
(The items in the square brackets are the "System Variables". Notice that there is not a system variable for the repository name. You will need to provide that when you set up the UDP)
Let me know if you need more information.