داشتن

In من کتاب دارم, the subject is the person who has the book. The possessed noun can be a plain object such as کتاب or a fuller phrase such as دو دوستِ خوب.

Use ندارم for “I do not have.” The form negates possession directly; do not construct ordinary possession as می‌دارم or نمی‌دارم. Those strings can have other literary or specialized uses, but they are not this everyday possession pattern.

داشتن also serves as the auxiliary in دارم می‌خوانم, “I am reading.” In that construction another inflected verb follows. A plain دارم with its possessed noun and a دارم plus می‌ verb have different jobs.

Common everyday Iranian third-person دارد becomes داره. Label this register choice, and preserve the written form in formal prose.