Latin doesn't have present continuous tense. How to express present continuous tense?
You express it with the present tense. The Latin present cano stands for both the English present "I sing" and the present continuous "I am singing". Only context will determine which English translation is more suitable for cano, but both English tenses can be translated with cano.
If you have a specific case where you want to make a distinction between the two English cases and the distinction matters, I recommend asking a separate question about it. For past events the distinction is easy to make (canebam ≈ "I was singing" and cecini ≈ "I sang"), but in the present the simplest approach is to use adverbs. But in many cases the English choice between present and present continuous is easily inferred from context and there is no need to emphasize it in Latin in any way.