For the real end-users (applicant / candidates), the effort is less;
- for existing candidates on career portal the change would be how they access their profiles / view the status of their application. You may need to highlight the "changes" from existing to new process.
- for new applicants, since they have to register their profile - the standard documentation could suffice.
For the staffing organization, however, which includes Recruiters, Administrators, Managers etc, the impact is larger. The procedure they were following earlier - with existing recruitment system, would change. This would require role-based training highlighting
- the new procedure - ERECRUIT standard documentation may help here.
- the changes along-with how the change would be beneficial to the staff (first) and then the organization.
By introducing some competitions with incentives could help in quick adoption.
Hope the above helps. The above process helped me on an engagement of deploying SAP E-Recruiting System where I worked on OCM role.