To put logos, you need the ID of the team. You can get it by checking the "show ID" option in the FM settings or via the editor.
Then you need to create 2 folders: small + large like this (C: \ Users \ PC Name \ Documents \ Interactive Sports \ Football Manager 2018 \ graphics \ logos \ folder name \ small)
In each folder, you will need a file "config.xml" that you create using an existing or using a software such as FMxml and you can put your logos in .png format.
If you have the id or name of the team and the logos, I want to do it to you.