Turnitin does not have packages for individuals. To get a Turnitin account for free as a student, contact your institution. Only institutions can purchase a Turnitin account then assign login credentials to its students.
Although it is illegal, you can also get a Turnitin account for individual use in Kenya by purchasing it from people who sell Turnitin accounts in Facebook groups like "Academia Research Writers". However, accounts purchased through such means can be closed any time by Turnitin.
Alternatively you can use ithenticate.com which is a plagiarism checker software owned by Turnitin and meant for individual writers, publishers and researchers.