Assuming the online school you are enrolled in is a Title IV school than yes, you may qualify for a federal Pell Grant.

A Title IV school is an accredited institution under the higher education act of 1965 as amended that offers federal student financial assistance programs.

In addition to grants you will also be eligible for federal loans, just as you would at any traditional Title IV ground campus institution.

You must first complete your FAFSA to become eligible for any federal loan or grant.  Thereafter your school will send you an awards letter outlining your financial aid options.  Contact your financial aid counselor for more details.