Concatenate

Click on the "Concatenate" box to define an aggregation field (the word "Concat" will be automatically added to the default value field and it will be disabled)

Select in the drop down box the SECOND column you want to use - the First one being the selected column

Fill the "Concatenation value" field with the SEPARATOR you want to use (example : space dash space ie " - ")

When this column is imported, it's value will be followed by the "Concatenation value" and then again the value found in the SECOND column you have selected here

Example : You can select column "Name" in the Destination list and here define the SECOND column as "First name" and using a separator of " - " obtain this result : "NAME - First Name"