Oui, je suis là.
Here's a breakdown:
* Oui: Means "yes"
* Je: Means "I"
* suis: Is the present tense of the verb "être" (to be)
* là: Means "here"
You could also use other variations depending on the context:
* Je suis présent(e). (I am present.) This is more formal and often used in a work setting.
* Je suis arrivé(e). (I have arrived.) This implies that you have just arrived at a specific location.
* Je suis ici. (I am here.) This is a more casual way of saying "I am here."
The best way to say it depends on the situation and who you are talking to.