Could be undercarbonated and pouring too fast, just pouring too fast, or it could just be overcarbed. Try turning down your pressure to about 4 PSI and bleeding the keg and then try to pour. It should pour pretty slowly. If it still comes out foamy your beer is overcarbed. If not, but it is still flat, it is undercarbed. If it comes out fine then your beer is good and you are pouring too fast.
If overcarbonated, unhook from CO2 and vent every day. You may be able to get it to stop where you want it carbonation wise, but more likely you will have to start the carbing process over. Until you get the hang of it, I suggest setting the gauge at 12 PSI and hooking it up to the keg of cold beer and forgetting about it for a week or two.
If undercarbonated, set the tank pressure to about 12 PSI and let it sit for a while. To avoid the beer coming out too fast, and causing it to foam up, you’ll have to lengthen your picnic line. I’ve had those taps not work at my usual serving pressure. The beer comes out too fast and foams in the glass.
A third possibility is that your tap line is too short and your beer is carbed fine. If that’s the case the beer will come out to fast and foam, leaving you with very little carbonation. Lengthen the tap line.
The tap line restriction and the serving pressure have to be balanced. Google “beer tap line balancing” for a ton of info available on the web.
This is all assuming that there are no odd blockages in the tubing or keg. If thats the case, you may have to dissasemble and find whats wrong.
Good luck and welcome to kegging. I promise it gets easier.