Actually we only use 10% of our brains. And a popular theory is that humans were able to use all 100% back when we were cavemen and then as time went on we invented things to help us so we evolved out of using all 100%. For example, we might of had super hearing to help us with hunting, but then we invented super markets so now we no longer hunt and thus no longer need that skill.
Actually,humans use 10% of their brains.10% of this are used in studies,research,communications,basically anything that Man had came up with.
You don't really need to unlock the other percentage because all you need to do is to learn back to its full capacity.That would mean thinking outside the box of perceptions,emotions and perhaps everything.It may seem slow to do so but what's great about this is to understand such complexity and simplicity of knowledge gained.That could be self-knowledge and any other types.
I recommend you to read some of Carl Jung's book since it gives some understanding related to the brain.
The idea we only use 10% of our brains is actually a misunderstanding of how the brain works. We use about that much at once, but the rest is dedicated to redundant systems so that we don't forget things every time we hit our heads. You don't need to unlock anything. You're actually using all of it, but you need to understand that using all of your brain at once would be a bad thing. If we did, suddenly we'd forget things whenever a section of brain cells died (which happens naturally and also when we have some kind of trauma like a bump on the head).
Actually we use about 35% of our brain when involved in the most complex of tasks. This is the total amount of all the areas working together. The different part of the brain have specific tasks they control or take part in. Even the areas of the brain that are being used don't have the entire part working on a task.
It is intriguing how little of our brain is used and makes one wonder what all the unused parts are for. Personally I think the parts that we don't use are because we lack what stimulates them. If we could only figure out what would stimulate these areas.