Steps to allow wordpress admin access to specific IP

Step 1: Login to your cPanel account.
Step 2: Select FileManager option under FILE.
Step 3: Click settings at top right corner. In the popup tab select the Document Root for your domain.
Step 4: Open the .htaccess file.
Step 5: Enter the below code to access from single IP address.

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Order Deny, Allow
Allow from IPaddress
Deny from all
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Step 6: Replace the IPaddress by your public IP address.
Step 7: Click Save option.