How to Enable Cookies in Mozilla Firefox Browser? Open Firefox Browser. Click on the Tools Menu and Select Options. The Options Dialog will Appear. Click the “Privacy” Tab. From the “Firefox will:” Selection Under History, Select the “Use custom Settings for History” Option. Check the Box next to “Accept Cookies From Sites” to Enable Cookies. Click the “Exception” button if you don’t want to accept cookies from certain websites. If You are Experiencing Problems with Cookies, Make Sure to Check the box Next to “Accept Third Party Cookies.” Select How long cookies are allowed to be stored by selecting the relevant option from the drop-down selection. You can keep the Cookies until they Expire, Until you Close Firefox, Or display an Alert Every time a website attempts to send a cookie. Click “OK.” To Save the Changes. Cookies are Now Enabled in Mozilla Firefox Browser.