Creating my own Kodi build

Quote from Bowie350z

First time doing my Kodi build using LibreElec. I have done it before on an Android box using File Manager HD to access the storage card to add picture files . What's the easies way to

do this using LibreElec.

thank you

If you mean customising kodi by sticking your own stuff in the kodi folder the easiest way is to use smb / samba. That way you can copy and paste directly in windows explorer.
Wiki guide: Accessing LibreELEC - LibreELEC
To access the whole kodi folder / whole storage partition:
LibreELEC