I have HEYNOW HNX4 Home game box S905X4, Is there a way to install ps2/ps3 games??
No.
As you can read here, PS2 and PS3 are not supported.
but I saw some vids on about YouTube installing ps2/ps3 on RetroArch which already installed on the device. Do you have info about this?
This is not the forum for your device, we do not support those companies, please ask whoever sold you the device and post your concerns there.
You have purchased a box that illegally uses Emuelec without authorization. These kind of companies make money with those devices, which is strictly not allowed. See here:
Retroarch that is cross-platform (windows, linux etc.) application to collect cores of emulators is absolutely NOT equal to EE or ES. EE w/ ES is specific for amlogic devices and included other selected and playable standalone emulators.
Btw, speaking of ps2/ps3, the device you mentioned seemed too sluggish and laggy to play roms. FYI