Hi Juan,
There is a pre-built DL-15 import format in TBC already and you can test/preview the DL15 data before you import... Open the 'Import Format Editor' from the small right drop-down arrow next to the Import command in the 'Home' tab, find the DL15 in the list, click test and load the file:
If you are happy with the preview, then use the 'Import' command to import the file. If a change is needed, click the 'Next' button in the 'Import Format Editor', where you can make your edits and save the format style. Then, use the 'Import' command to import the file.