Pics from computer to mobile phone

since you posted in android, i'll assume its an android smartphone...

tether the phone to your pc via a usb cable
mount the sd card as a disk drive (either in notifications or in settings)
on the computer open up the sd card drive (or internal memory drive)

/dcim/ is where photos are stored when you take pictures, however you can have a folder named anything if you just want them to show up in photo viewer.