How do i change the bit on router?

On my older Sears router there is a lever on the base near the collet nut that you slide to engage the motor shaft to lock the motor shaft for bit changes. On newer models you may have a button or different mechanism to lock the shaft. After the shaft is locked you can use a small wrench to loosen the collet nut, usually by turning it counter-clockwise (viewed from the base). Once the nut is loose the bit should slide out (sometimes the bit is stuck in the collet and the nut may need to come all the way off to get them apart). Just replace the bit with a new bit with the same shaft diameter, tighten the nut, and you are set. If the new bit has a different shaft diameter than the old bit you may need to change the collet also (in general, different collets are used with different bit shaft diameters).

There os a lock to lock the bit from turning and has alen wrench type key to open it