Normally, the corresponding author will be one who sends the material to the journal (the paper files, figure files, cover letter, biographies, etc.) The corresponding author will normally be the author of the cover letter / cover email. Note that the current state of the publishing field is such that many journals use a totally online submission and review process while others still use ad hoc emailing of files and messages. If you are engaging an online system, you will be directed to enter information or upload files. If you are emailing the files directly to the editor then make sure you use a common format such as pdf or Word doc and descriptively label the file names.
On the paper itself, be sure to include all of the correspondence information for each author on the cover page: author's name as it should appear in print, affiliation, postal address, telephone and fax numbers, and e-mail address. If the journal uses a double blind procedure then this information will be deleted prior to being sent out for review.