Restrict IP access to your admin section
Editting your .htaccess
You should find a .htaccess file in your root folder (or catalog depending on where you installed your store)
Edit this file using Notepad or similar
Add the following to the top of this file
order deny,allow
deny from all
allow from 888.888.888.888
If you want to allow access from multiple IP address or domain names then add
allow from 999.999.999.999
allow from 000.000.000.000
Obviously you need to replace the above with your IP addresses.
To specify a domain name use
allow from .yourdomainname.com