How Can I make Niyyah (intention) for I’tikaf?

 How should one make niyyah for i’tikaf?

One makes it wajib for himself by saying “I took the vow and made the intention for i’tikaf to stay in such and such masjid for such and such long”.
 It is also enough to make niyyah in your mind, by just thinking about doing it with i’tikaf intention, even If he doesn’t say it loudly by his tongue.
Once he made his niyyah (intention) for i’tikaf, he may is not permitted to leave the masjid except for darurah situations such as; for taking ablution or ghusl, for using the loo. Otherwise, his i’tikaf would be spoiled and void.