Follow the simple steps given below :
Step 1 : Click on Settings option situated at top right corner of screen.
Step 2 : In General tab look for 5th option "Browser connection".
Step 3 : Click on Always use https option.
Step 4 : Save changes
After completing procedure you will see https://www.gmail.com instead of http://www.gmail.com. This indicates that you are browsing gmail on secure connection. It makes your connection encrypted by using SSL/TLS protocols so protects you from the eavesdropping and intercepting your data by someone for malicious purpose.
You can also enable secure browsing in facebook. Read how to make facebook connection secure here