When you define a new template, there are two lines visible at the top of the report window, one labelled T, and one labelled S.
In the T line, put the characters that you want to use to trap the line on - using the exact characters themselves or wildcards like Ã for "any letter" and Ñ for "any number".
In the S line, select the areas of the line that you want as fields, by clicking and dragging the mouse. These should appear in black.
Then when you click OK, you should see a chevron in the left margin next to every line that matches the Trap expression, with the fields highlighted as per your Selection choice.