When you want to duplicate the feature(s) of a supplied template file, the first thing to do is open a copy of the template and investigate how it was done in the template. You can examine that parts of the layout while in layout mode to learn what options where selected in setting up the layout and also to identify the table occurrence names referenced. You can then open Manage | Database and investigate the relationships and field definitions.
Have you done that yet?
I find the technique used is a filtered relationship that exploits a computed multi-value key so that selected values in the radio button field will act to filter the list of records displayed in your portal.
Here's the relationship you need (subsitute your field and table occurrence names for mine):
YourMainTable::Similars = SimilarContacts::MultiKey AND
YourMainTable::PrimaryKey ≠ SimilarContacts::PrimaryKey
SimilarContacts is a 2nd table occurrence of YourMainTable. You create it by Selecting YourMainTable in Manage | Database | Relationships and clicking the button with two green plus signs to duplicate it. Then you rename it and link it to YourMainTable.
PrimaryKey should be an auto-entered serial number so that it uniquely identifies each record in YourMainTable.
Similars is a calculation set to return text:
Case ( RadioButtonField = "Center Name" ; CenterNameField ;
RadioButtonField = "Company" ; CompanyField ;
RadioButtonField = "Last Name" ; LastNameField ;
RadioButtonField = "City" ; CityField ;
"" ) /* last parameter, ; "" , may be omitted if you prefer */
MultiKey is a calculation field set to return text: List ( CenterNameField ; CompanyField ; Last Name ; CityField )
Note: this is a farily sophisticated thing for a total beginner to tackle. Don't hesitate to ask more questions if this isn't completely clear or you try it and it doesn't work.