You can delete a column in two ways -
1) By using suggestions on right panel
Step 1: When you create a new connection, for example as shown here in Connect To hadoop article, you will get to Preview Screen.
Step 2: On preview screen, select the column which you want to delete. As and when you click on the column name top bar , you can get deletion suggestion in suggestions tab of right panel.
Step 4: You can select the option to drop and click on it. It will apply the selected delete operation on the column and will delete the column.
2) By using drop down list
Step 1: When you create a new connection, for example as shown here in Connect To hadoop article, you will get to Preview Screen.
Step 2: On preview screen, select the column which you want to delete and click on down arrow.
Step 3: Click on "delete column" from the drop down list in "Modify Column" section.
Step 4: As and when you click on delete column, the system will apply the operation and will delete the rows.