1) Remove ALL electrical power to the laptop. The AC adapter (Charger) and Battery.
2) Open the laptop, press the Power On button, and hold it in for a count of 5 seconds. (Removes residual power)
3) Close the laptop, turn it over. Remove the 'Thermal Door'. This is a large panel on the back of the laptop. There are several Philips head screws to remove, going around the outer perimeter of the panel.http://members.aceweb.com/gregg1/acer/Inside_Acer_Aspire_5315.html
Here you will see the panel removed, and the ram memory compartment marked.
Handle a Ram Memory module ('Stick') by the body, and refrain from touching the gold plated contact pins on the bottom.
The body is coated with a see-through protective plastic.
Your body carries Static electricity, and Static will fry out (Short Circuit) the hardware components inside a computer.
There are two ram memory slots.
There are two metal clips that hold a ram memory module in place.
One on each side of the ram memory module. Look at the sides of the ram memory module, where the metal clips press against.
Each metal clip has a rounded 'knob' that fits inside a Notch, on the sides of the ram memory module.
Use the fingernails of one hand, to ease out on the 'knob' of one clip, while doing the same to the other clip, with the other hand.
(Ease the clips out away from the ram memory module)
Once the clip's knob is free from the notch of the ram memory module, the ram memory module should slightly pop up on one side.
Lift the side that comes up, to a slight angle, then keeping it at that angle, remove it.
DO NOT lift straight up on the ram memory module, or you'll damage the connecting pins in the ram slot.
(And the gold plated contact pins on the ram memory module)
To replace line the ram memory module up at the angle you removed the old one.
Slide it down in the ram slot.
Then gently spread the metal clips, and ensure they are seated in the notches at each end of the ram memory module.
For further questions please state in a Comment.