Hi,
You just have to rename the file downloaded from LiveATC.net.
For your example, the filename should be EHAM_APP(100).PLS and Laap will integrate it in its database.
In general, Laap will recognize files with that format : OACI_TYP(VOL).PLS or OACI_TYP(VOL).MP3.
If needed, feel free to contact Laap support directly from the contact page on the site.
Regards,
Frederic