I did the following, which may also work for you.
* go to the ootpmods site, at
http://ootpmods.allsimbaseball.com/files/
* download aio_2018.zip. For me, I simply clicked on the file and it was downloaded to my "Downloads" folder as aio_2018.zip.
* open the zip file. I believe that Windows can read zip files without problems (I'm not on Windows, so didn't confirm
)
Inside the zip file you should see a folder called custdata. Within that there are four more folders: ballcaps, fg_files, logos, and jerseys. You can either copy the custdata folder itself onto the folder "custdata" that OOTP created on installation, or do each folder -- or file -- individually.
The custdata folder should be found at "Documents/Out of the Park Developments/OOTP Baseball", if you are running on Windows 10. See
http://manuals.ootpdevelopments.com/index.php?man=ootp19&page=installation_locations
to confirm.
Note that, at least for the logos folder, the AIO has (possibly out of date) duplicates of the MLB logos, so you may want to "not overwrite" when you extract the files from the .zip archive.
Hope this helps.
-kr-