One of the most important things for beginners to remember about the present tense (beginners can worry later about what "indicative" means) is that English has more than one way to express what is expressed in this one Spanish verb form. Take a simple sentence such as ella habla. That sentence could be expressed in English using not only the simple present tense and saying "she speaks," but also by saying "she is speaking" or "she does speak." When you're translating a Spanish present-tense sentence into English, you need to use the context to tell you which English form to use. Thus "ahora ella canta" would usually be translated as "now she is singing," but "ella canta los lunes" would more likely be translated as "she sings on Mondays." (Note that it is possible in Spanish to say ella está cantando, which is a word-for-word translation of the English "she is singing." But that form isn't used nearly as often in Spanish as it is in English.)
Following are the different ways the simple present tense is used in Spanish. Note that in general the same ways are used in English.
To describe something that is happening right now: In English, these are often translated using the "-ing" form of the verb. Examples: Ella canta. "She is singing." Él come. "He is eating." Anda a la casa de su abuela. "He is walking to his grandmother's house." Estoy en casa. "I am at home."
To describe something happening in the near future: In both English and Spanish, the present and future tenses are often interchangeable for this purpose. Most often a time element is indicated in the sentence for this usage of the present. El tren sale a las ocho de la noche. "The train leaves at 8 p.m." La clase comienza temprano. "The class begins early." Vuelo el lunes. "I am flying on Monday."
To tell a general truth or describe an action that is repeated habitually or regularly: Such statements generally describe events or conditions happening in the past, present and future. Él toca el piano. "He plays the piano." Duermo mucho los sábados. "I sleep much on Saturdays." María escribe bien. "María writes well." Mi hija es inteligente. "My daughter is intelligent."
In a narrative, to tell of the past: When telling a story or giving an account of an event, it is sometimes possible to provide the narrative in the present tense. Va al supermercado y pega un tiro al gerente. Entonces huye a México. "He goes to the supermarket and shoots the manager. Then he flees to Mexico."
In questions, to get instructions: In English, such a usage often uses the verb "do." ¿Pago ahora o después? "Do I pay now or later?" ¿Dónde cambio de ropa? "Where do I change clothes?"
In some cases, to state conditions or hypotheses: The present indicative is often used after si, the equivalent of "if." Other verb tenses can also be used; generally, the present indicative is used when English also uses the present indicative. Si salgo, estaré feliz. "If I leave, I will be happy." Si tienes tiempo, ve al Perú. "If you have time, go to Peru." Cuando nieva, no puedo trabajar. "When it snows, I cannot work."
Again, context is the key to telling you which way a particular verb is being used. As long as you remember that trabajo, for example, can mean either "I work" or "I am working," you should have little difficulty in learning the uses of the present tense.