When in gantter you will see  the WBS does not allow edits due to this being the outline numbers. 

You can create a custom column to create your own. 

Hey Roberto,

So unfortunately importing and exporting right from sheets or excel into gantter is not a function the current gantter possesses. However we are going to be putting this feature into a future release of gantter because it is one of our most requested features. 

There is a work around though so you don't have to write in every task you already entered in on a sheet into gantter manually. Go into the google sheet select all the cells you want to copy in and hit copy.

Then go into gantter and select the number of cells you will need to paste what your putting in.

Then you have to paste the tasks in using gantter's paste icon which looks like this: (sorry for the poor image quality) 

If you use your own computers paste option of google chromes it won't work it has to be gantters from the gantter toolbar up at the top. Let me know if you have any followup questions and I really hope this helps! : )