how can i reapply for a job that i already sent my resume to?

Answer 1

You can apply as many times as you like. Just do it the same way you did the first time except that you won't need to give them your resume again since it will be on file and usually resumes are kept on file for at least a year.

Answer 2

Just reapply asking them if they have received your application+resume. Some companies have a wording"shortlisted candidates will only be entertained or need not apply" that means when they don't respond a thank you for applying with them you are not shortlisted as possible candidate.