When do you use it?
To talk about an event in the future that is not certain or for spontaneous decisions.
How do you use it?
Put "will" in front of the infinitive form of the verb.
For example: I will play tennis tomorrow. OR use the contracted form: She'll phone next week.
Negations: Put "not" in between will and the verb. I will not come tomorrow. OR use "won't" - I won't come tomorrow.
Questions: Will she arrive by six?