Heres how i would do it. Heat up some of the juice (not too hot as this may release tannins and stuff) hot enough to stir in sugar until it dissolves. Id rec 1-2lbs of sugar for 5 gallon batch.
Again, if you "steep" the whole fruit at high temps, you will release tannins and might lead to off-flavors. Another option is bag the fruit and put in fermenter, then pour the warm juice/sugar mix over it, followed by the rest of juice.
Just having the fruit floating in there will change color and taste significantly. If you want, you can squish fruit bag against inside of fermenter periodically to release more goodness.
Ive always used frozen, but even if you have fresh berries, I would freeze until brew day, for sanitary reasons and bc it'll break the capsules and cause more flavor in cider. (in the past ive used 2 lbs of mixed berries like this in 6 gallons of skeeter pee, and the berry flavor comes thru the lemon tartness, so in apple you should def taste the berry flavor)
Use beer yeast, Nottingham or s-04, because it will leave alot more fruit flavor and sweetness. Pitch and wait two weeks.
You should also think about if you want it carbonated or still, bottled or kegged?