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