You will find a notable learning curve by skipping from rank 5 to rank 8 combat. its very different.
My advice, run a few bombs (enough for 1x base kill) and edge skirt to a base for 1x base kill, F4S are fast enough to get this fairly reliably before then turning back into the fight, until you get more confident with jet based combat, I would stick with the Aim-7F Sparrows as your main weapon, these are SARH missiles, meaning you need to lock onto a target with your radar and maintain the lock throughout the launch, do note if the target is too low, then the missile will likely be defeated by “multipathing” and the missile will crash into the ground. Go for targets that are distracted in a fight and engage them. Do note that locking onto them with your radar will light up their RWR so they will have warning. Alternatively, you could use the Aim-9Hs which are rear-aspect IR Missiles to engage targets to, again, I would aim for people distracted.
Radar:
You have 2 radar modes. SRC and SRC PDV HDN.
SRC is good for targets in most aspects but only at higher altitudes and will struggle with targets near the ground, the other mode (for the sake of ease, i will refer to as PDV) is a mode that only works when the target is flying directly towards you, but will work at any alt.
You also have ACM mode which just locks onto anything directly infront of the nose, very handy for a rapid lock and then HMS mode which is ACM but you can control.
On the right hand side of the radar panel, when you lock onto a target and have a missle selected, you will see 3 lines, 2 short 1 long. those are a range indicator, the top small line is the max range of the missile, the bottom small line is the min range of the missile and the long line is the current range, I would advice Against firing near the top of that window, but if you aim for the bottom third or so, you can be reasonably sure it will hit unless the missile is defeated
Maintain high speed as best you can, and avoid unncessary dogfights, though the F4S is one of the better F4s for dogfighting in.
Do also be careful if you get uptiered, at 12.0, you can see 13.0 aircraft that are slinging ARH missiles, this is why I would advice sticking much lower to the ground and terrain mask wherever possible