To use the API you'll need to use GET.
Examples:
If you have the tt-ID you can use https://api.swetracker.org/?title=tt0107989

If you only have a title you can use https://api.swetracker.org/?title=batman+begins

For a more exact search when searching with only a title you can include a year or exact-parameter like https://api.swetracker.org/?title=batman+begins+2005&exact=true

If you only want to fetch the poster you can use https://api.swetracker.org/?title=tt0107989&poster=true
This will output someting like
Legal EMAIL US 17951 hits so far