Roll up time worked to parent table

I was approached by a community member that was wondering how to calculate data in the time worked related list and then put that result in a field on the incident form.

Now there are 2 ways to do this. If you just want to see it, you can easy do like this: 

Right-click on the column you want to calculate and choose "List Calculations".

There you can choose the Total value and vola, you got the data at the bottom.

But then, if you might want to do reports on this value or something else, you want to put this data in a field on the incident form instead.

To read about the second way follow this link to the community: 
Roll up time worked to parent table