You need :   
White candle 
Holder of salt   
Place the candle in the middle of the room. 

Sprinkle the salt in a circle deosil around the candle.    
Light it and say :   

Creature of wax, Creature of fire,
Listen to me, Hear my desire 
Cleanse this room By the power of three 
And blast away all negativity 
With harm to none So shall it be !   

Leave to burn for at least 1 hour