1. Login into the vesta control panel.
2. Click on WEB in top section.
3. Move the curson on the domain on which you want to apply SSL certificate.
4. Click on Edit.
5. Check SSL Support and check Lets Encrypt Support to use free SSL certificate.
6. If you have your own SSL certificate then paste the certificate and key in the boxes (Leave them if you are using Lets Encrypt).
7. Click on SAVE.