It is given in the defination of electric potential in a website that we bring a charge from infinity to that point slowly(without acceleration). But if the charge placed at infinity is at rest or moving towards a random direction then how can we place the the charge on the required point without acceleration. May be I have some misconception , please clear my concept. I don't have much information so please help me out from this problem.
An external force is applied to the charge which varies so as not to change the speed of the charge.
That external force can change the direction of motion of the charge but not change its speed by acting in a direction which is at right angles to the direction of the velocity of the charge.
This would mean that the force does no work on the charge and hence does not change its speed even though the charge is accelerating because it is changing its direction of motion.
Obvious to move a charge from infinity without accelerating it is not a very practical proposal if the charges attract. You can also let it fall in, measure its speed and subtract the kinetic energy. For the repulsive case I see no issue other than that infinity is very far off.