Calculated Column question

Hi ,  I am pretty new to Power BI, simple question

I have 2 excel tables that I joined (1 to 1)  I just want to create a new column and add value1 from table 1 to value 2 from table 2.   

When I try to add in the column for the 2nd value,  It wont allow me to start typing in the new table and column.  Any help appreciated, Thank you