How do i Merge 2 columns i have added into a table

Hi

How do I Merge 2 columns that I have added into a table using the Add Column function?

I did not add these columns in the Transform Data area so when i go into the source table using transform data the 2 columns that i added are not there.

I need to add 2 columns together where one of the columns has blank values for some entries. 

the desired value from the below extract will be a new column with "VL01" in same for all entries.