Always remember, Perspective is Reality. That is what the game keeps telling you but it may seem confusing how to execute it while playing. There is one general rule to keep in mind on how to make things bigger in Superliminal.
This guide will help you make things bigger so you can use all that brainpower to actually solve the puzzle because this mechanic should already be second nature to you.
Holding the Item
Hold the item you want to enlarge first by left-clicking the item. You do not have to hold the left mouse button and just left-click again if you need to drop it. Once you are holding the item, make sure you have some space to make it bigger by either putting it in another room or placing it as far as you can from where you are standing.
Basically, if you start holding an item at the closest range possible, it will be tiny and if you reel back to the wall while holding the item and place it down towards the opposite side as far as you can, it will make the thing bigger. As long as you follow the rule where you use your perspective by placing it far from you while holding the item, it will already be bigger than when you originally held the item.
Making Things Smaller
To make things smaller, it will just be the opposite of what was explained before. You can take an item that is quite far away from you and grab it. To shrink the item, you will need to place the item somewhere near you, preferably a table you can put it on or even just the floor you are standing on as long as it is near you. Through perspective, the item gets smaller the closer it is dropped from your eyes.
Most of the early levels (such as Level 1) will involve puzzles in enlarging or shrinking things to progress. Once you get into the higher stages with more mind-boggling puzzles, you should already be quick in making these items bigger or smaller because there will be more game mechanics introduced in other levels in the game.