Hey Erglis,
Welcome to the area. I too fish more from shore around Kingston than in a boat.
The best places I've found are different depending on the type of fish you're looking for.
The salmon and trout should soon be coming in at the Hydro Plant, just outside of Bath as well as Kingston Mills. It's always a good time and fish. Personally, I use gummy bears but at the Mills, I've seen people throw everything in there.
I used to spend quite a bit of time fishing at the Portsmouth Harbour too. At the end of the far pier, dropping minnows straight down have produced some fantastic bass and pike. Getting minnows now, around this area though is almost impossible
At the begining of this pier, you'll see a break wall. Casting crank baits early evening, I've caught pike in the 10-15 lb range and walleye over 6lbs. This too is the case near the gas pumps close to the building at night. If you're an eel fan, that's the perfect place too.
As Hay Bay Larry has pointed out, across from the Kosa plant has (or had) fish. I used to fish this area a lot but they pretty much shut down the stream and the trickle that does come out now just doesn't seem the same to me so I haven't returned. If it does contain some steelies, please let me know. I;ll have to return.
Again, about the hydro plant, I was there last weekend. A lot of big fish were jumping but too far off shore. I'm not sure if they were trout or salmon but pretty sure they weren't carp. It usually has a lot of them around and huge ones at that.
I hope this helps and good luck.... if you're having luck, please share.
CHEERS!