firstly you need to copy your gta 5 game directory for a clean backup. since your new, download the auto install version and run it.
once you create a rockstar id then you can just download a copy straight from them instead of installing with disks. YOU WANT A BACKUP SO YOU DONT NEED TO DO THIS IN CASE SOMETHING HAPPENS!!
If you dont have the space for a backup then i suggest limited modding
And you may have to watch a video multiple times. not including pausing and rewinding the video. make sure you watch every second of the parts you need.