Place the pieces steel/iron onto the magnet (one piece per magnet) until they are are touching at the desired position for welding them together.
If using an on/off magnet ensure the magnet is switched off before use, then align the pieces of metal in the position required, then turn on the magnet. When you need to remove the magnet again you will need to switch the magnet off and then carefully move the magnet away from the material you have been working with.
Removing the 90 degree angle weld clamp magnet
When you have finished using the magnets in any way you will have to knock the magnets off the pieces of steel/iron sideways with a rubber headed mallet to remove it.
If you have a 90° weld clamp magnet with a cam lever you will need to use this to pry the magnet away from the materials surface before lifting it away.