Determining electric purchase and self consumption

Hey Guys I have a problem with an excel task

Can somebody tell me what I should do with the task 4 ?
Open the "SLP load profile - household H0". You will find a 15-minute load profile in
Active power KW before. When importing the opening, make sure that you do not use the "comma" as a
Select separation option, otherwise the values ​​will not be imported correctly.
2. Insert a new column between B and C, this will now have the name C.
3. Click in the third row of the new column and add the date and time
together approximately = sum (A3 + B3). Now you will see a point number in the program
represents a point in time.
4. Now format the cell in a format that gives you the date and time
displays at the same time. The result looks like this for one cell (01/01/2011 00:15)
5. Click the cell (here C3). Now move your pointer to the lower right corner
the cell. A thick point will appear there. Double click on this point.
Now the previously inserted formula should have been copied to the cells below.
Check to see if this has happened. There are around 35,000 lines.

The problem is I cant post an image what I have done lol
Has somebody an idea ?