The difference between the symeteric and assymetric encryption process is the keys. For the symeteric both people have the same keys. For asymeteric everyone has your public key but only you have your private key. This means that anyone can encrypt the message but only you can decrypt it.
The steps of the encryption process start with you makng your message and putting it in your parteners public key. After this in your repo. Then you go to parteners repo and get the file. You run it through your public key and aare able to read it.
If you share you seceret key then anyone can read you message. They can see anything that you send. This could be your personal information which you would not want made public