Adding the roms

I got everything set up. Once that i added Noobs on the SD card, i went into the OS folder and removed all of the os like Libreelec and Rasbain and added the new updates of Lakka and LibreELEC-RPi4.arm-10.0.2.img. Everything went fine. Look trough it all to get a hang of it all. So now, its the roms. I have many roms saved on the laptop, and i got them from safe sites. Got the roms on a usb drive. how do i play them on lakka. Like on Retropie which i had error problems on that. Do i have to install emulators to lakka, like you do on retropie…