The Skip Barber is pretty difficult to come to grips with (literally) and if you're anything like I was you'll spend a lot of time on track with the back end of the car pointing in the direction you wanted the front to go. My personal preference in sims is turn off all assists and just learn the correct technique for the car, but of course your kilometerage may differ. In the case of the Skippy there are a couple of essentials: don't carry too much speed into corners (ie slow in fast out); do as much braking as you can in a straight line; get used to heel/toe downchanges and don't do them in turns; learn to love lift off oversteer etc etc. I'm sure others will have additional pointers. There are a few setup changes you can make to make the car a bit more comfortable, such as dropping tyre pressures and increasing front caster, but it will probably remain a frustrating car to drive until one session it will just click and all of a sudden you're enjoyably competitive.
Many people swear by the Spark F3 as a more enjoyable low powered open wheeler, and it's certainly far less twitchy and easier to throw around than the Skippy (which by all accounts is designed to punish incorrect technique).