Computers only appear in Computer Rooms and Cipher Rooms. They are always aligned against either the north or south walls of the room where they appear.
Computers are the only Buggable Furniture in both the above-mentioned rooms. Since bugging these rooms gives the best possible Surveillance Quality (+8% and +12%, respectively), Computers are by-and-large the best possible piece of Furniture to place a bug in, if you can find them.
To bug a Computer, walk up to it and press the "F3" key. You will need at least one Bug remaining in Max's inventory to do so.
You can hide behind a Computer even without crouching. It is impossible to jump over a Computer.
Computer vs. Terminal[]
Note that the use of the term "Computer" to describe this piece of furniture can be considered outdated and may be confusing.
A 2x2x2 meter cube standing in the corner of a room is what we would nowadays call a "Mainframe" or at least a "Server", but the game refers to it as a "Computer". This piece of furniture can only be Bugged - you cannot interact with it in any other way.
On the other hand, the desktop-variety computer, the kind we're all familiar with, that has a keyboard and screen and all that, is referred to in-game as a "Terminal". That is the piece of furniture that can be Hacked into by Max to retrieve information.
remaining in Max's inventory to do so.