Step 1: Right Click on the File/Folder you with to encrypt.
Step 2: Select "7-Zip" -> "Add to Archive".
Step 2: If desired, you can change file name for your archive.
Step 3: In the "Archive format" drop down menu, select "zip".
Step 4: In the "Encryption method" drop down menu, select "AES-256".
Step 5: Type in the Encryption password in the password fields.
Note: Tutorials on how to choose a good password is located at https://docs.rice.edu/confluence/display/ITTUT/Passwords
Step 6: Click "OK" and now the encrypted zip file will appear in the same directory/location.
If you are e-mailing, it is recommended to use an alternative form of communication (e.g. phone call) to share the password used to encrypt the file. For example, do not send the password in the same email as the encrypted file.