when functioning as a verb, 'using' refers to the action of making something use of something else. It indicates that the subject is actively benefitting from or making use of the provided object to execute some sort of action.
1. She is using a chair to reach the top shelf.
2. He is using a calculator to solve the equation.
3. She is using her knowledge of the language to translate the passage.
It is important to note that this usage of 'using' implies an intentional, active action on the part of the user; however, in some cases, particularly if the action is lacking in intent and/or not deliberate, one may use the verb 'utilize' instead.