If the verb in the predicate of a sentence expresses the existence of something, such as IMASU (to be, to exist), NI indicates where something is or exists. For example, "I am at the station" is ...

I am 15 years old - Tengo 15 años. When you talk about something that happens regularly or describe what something does or is doing, then you use the present tense. The first part of the verb you ...