If necessary, fabricate an adapter for connecting 6.3 mm plug to 3.5 mm socket. To do this, buy the 6.3 mm socket (required for stereo), and from the evil of headphones, cut the 3.5 mm stereo mini-plug (monaural, microphone is not necessary). Connect the homonymous socket contacts and plug together.
Disconnect speakers (if any) from the mains, then remove their plug from the green socket of the sound card. Instead connect the headphones. The laptop socket might not be green, and silver, and next to it there may be a pictogram symbolizing the headphones. Also may look nest old sound card for desktop computer. If the laptop has built in speakers, after the headphones they will automatically turn off.
To the Jack located on the rear of the machine, connect the plugs are uncomfortable. If the housing is equipped with front sockets, open it (with disconnected machine), locate the red and green plugs, pull cords with them through the slot in the rear wall, and then connect them to the jacks of the sound card having the same color (don't mix them). After that connect the headphones to the front green Jack.
If to the computer instead of separate columns connected to a monitor with speakers, find it on the front or side of the headphone Jack. Connect the headphones to it. After that, the built-in speakers of the monitor will turn off automatically. Same jacks are available on some active speakers, but much less frequently. With this connection to adjust the volume not only in the mixer of the computer, but the knob located on the monitor or speakers.
In all cases, do not expose too much volume is bad for your hearing. You can be guided by the following criteria: the volume is normal, if, despite the fact that from you wearing headphones the music, you can still clearly hear the speech coming from the quiet sounding receiver or TV, located three meters away from you.