Citation help in APA format
APA follows the basic format of Who-When-What-Where. In your case, it will be:
ACT. (2018, October 18). Condition of College and Career Readiness 2018. http://www.act.org/content/act/en/research/reports/act-publications/condition-of-college-and-career-readiness-2018.html
Some details:

Who? There is no individual author named; we shall thus take the authoring organization, ACT.
When? The report is from 18 October 2018; use the format YYYY, Month Day for the publication type 'report'.
What? The title of the report (Condition of College and Career Readiness 2018).
Where? The URL where the report can be retrieved from. (Note: The additional words &quot;Retrieved from [URL]&quot; used to be mandatory in earlier versions of the APA Style Guide, but not in the current version anymore - see, for example, here.)