Yes, recommendation letters are completely confidential and students can NEVER view the contents of the letter.
Once you upload a rec letter, it's attached to the student's profile and they can see their various rec letters listed under their "Documents" tab (within their "Profile"). However, they cannot download or view them, so they remain absolutely confidential.
The reason they are attached to their student's profile is that then allows them to use the letters for many different scholarships (without having to pester the recommender each time).
There are three options for uploading rec letters:
You as a counselor can upload rec letters directly for your students. You can do that through this link (after creating an account): https://app.goingmerry.com/counselors/students
Your student can invite you or someone else to provide a rec letter for them by inviting them directly. They need to go to their "Profile" then "Documents" then "Request Rec Letter". The recommender is then sent an email with instructions on how to upload their letter.
Your student can upload rec letters you provide them in paper form or digital form (e.g. email). In this case, students obviously are able to see the rec letter contents since you purposely provided the document to them.