Can I import from excel and then populate user accounts with the imported data?

Hi, I am working on a holiday booking system at present. I want to import the holidays from an excel document and then take this data and populate existing user accounts with it. Note: importing the excel document is already in place but it does not link to user accounts. The user accounts have been created in the app already.  The app currently has microflows etc that populate calendars and create an approved and pending leave requests list. I read a few existing questions relating to creating user accounts via import (that will be something we take on in the future for our app), I am just not sure what steps I need to go through to complete this process.  How to make the link between Accounts and imported data.  Below is a snip from the domain model.    
1 answers

If you have usernames (aka email addresses) in your imported data, you can create system.user entities (or administration.account) with it.


Be sure to:

 – set a password

 – make sure there are no duplicates (usernames should be unique)

 – attach a role to the system.user entity

 – set the boolean active to true