The usual method is to go change your secure_base_url from http://www.yourwebsite.com/ to https://www.yourwebsite.com/ and then drop down to the two checkboxes, one is something along the lines of “Use Secure in Frontend” and save the configuration. Don’t get all trigger happy and change “Use Secure for Admin” yet as you can lock yourself out.
Go log yourself into one of your test user accounts on the front end and you should see your secure access indicators turn on in the web browser of your choice. Same thing after you reach a certain point in the checkout process, after viewing your cart and then telling Magento you want to Check Out, it should once again switch into secure mode.
Once you have this occurring, then go back into your system config and check the “Use Secure for Admin” checkbox and you will now have secured access to your Admin panel.