Start with Trailhead, there are specific Trails for Admin (and other) certifications. Navigate to <https://trailhead.salesforce.com/>

Under Credentials, select Certifications.

Select your desired certification. Here we select Salesforce Administrator.

This will recommend several Trails and Trailmixes to help you prepare for the exam.

salesforce.com

guide provides a step-by-step process on how to prepare for the Salesforce Administrator Certification Exam. By following the outlined steps, users can access valuable resources on Trailhead, select the relevant certification track, and log in to access specific exam preparation materials.