Tips for touch up paint

I just recently got my first scratch and it is down to the metal. After getting super pissed and heartbroken since it happened in the gayest way possible where something flew off a car next to me on the freeway and totally attacked my brand new truck. I went to the dealership and got the touchup paint for my truck but I am just Curiouse if anyone has any pointers or special techinque for me befor I actually paint over the scratch. Thanks for your knowledge ahead of time

 

Just make sure to get it on there before the rust starts creeping in.