I have some artifacts in Artifactory (OpenSource):
I can download an artifact from using jfrog CLI:
jfrog rt config --user=
If you wish to do it from a Jenkins groovy file, you could use:
def downloadSpec = """{ "files": [ { "pattern": pattern, "target": "", "flat" : "true", "sortBy": ["name"], "sortOrder": "desc", "limit": 1 } ] }"""