How do I install car mods and visual mods on the Complete Edition?

[tesla318]

I just bought the Complete Edition on Steam and I want to put in some car mods and good visual mods.

But I'm finding all these stuff on Google saying that 'YO YO YO YO YO YOU NEED TO DOWNGRADE TO 1.0.7.0 TO USE MODS' and 'I'm using mods on 1.2.0.0' and that stuff.

 

So do I have to downgrade the game to use any mods or what? And can I use the mods on all 3 stories(original, TBoGT, TLaD)?

 

And if anyone can, please give me basic instructions on how to download the mods properly...… I find the modding quite different from GTA V where all I needed to do is install Open IV.(Oh yes saying about it, can I use OpenIV on The Complete Edition too?)

 

Thank you very much in advance. I'm not so familiar with computers yet......