To install SP you just drag the files inside SP folder into 
Grand Theft Auto V\mods\update\x64\dlcpacks\mpimportexport\dlc.rpf\x64\models\cdimages\mpimportexport_male.rpf\mp_m_freemode_01_mp_m_importexport_01

For FiveM just drag the stoneisland folder into your resource folder and go to server.cfg and write start stoneisland