Convert username to text field

Hi

I have a custom list in SharePoint 2013 On-Premise.  I have created a SP2010 workflow so I can make use of ILoveSharePoint.  The workflow basically creates a site, a security group and adds a user to this security group based on the on the information from the custom list.

Here is the information I need and what it is used for.

Firstname and lastname (Text fields):  This is used to create the URL e.g. http://sharepoint/lastnamefirstname

Login name (Username):  This is added to the security group created.

This works well, however....

Ideally, I only want the to enter the login name and use this to calculate the firstname and lastname.  How can I achieve this using the workflow? or perhaps this can be achieved using calculated fields.

Marc Collins www.QGate.co.uk