Hi My A Column data is Title and B Column is sub classification Column A, I need title Column A to repeat for all respective rows of B Col

Select used area of column A and pick Blanks From Goto special and enter "+ or =" then do select adjacent row(probably upper row) then do shift +Ctrl +Enter

this action will repeat all the above values as you desired (as a formula) then you need to select the all area and paste it as value