To become a Certified Salesforce Administrator, you have to clear the Sales Administrator Exam (ADM 201):
Step 1: Enroll an online training course for Sales Admin 201 Certification.
Step 2: Visit certification.salesforce.com and register to take the Salesforce Admin 201 Certification.
Step 3: Pass the exam to become certified.
If you are preparing for the Salesforce Admin 201 Certification exam, you can take up this Salesforce Training course by Intellipaat.
You can watch this video on Salesforce by Intellipaat to know about Salesforce certification in a detailed manner: