Here are some helpful links regarding resources:
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[How-to] Install a FiveM resource / Script
[Tutorial] Merge Meta (Multiple Cars in 1 Resource)
[How-to] Add Car Parts from Add-on Vehicles to your server
Tutorial fiveM Resources , Add-ons , PED's (Skins)
[How-to] Split Vehicle YTD Files to Avoid 16Mb Stream Limit (No Texture Compression)
[How-to] Change the spawn name of a addon-vehicle