Tense is generally determined by context but as a basic rule past tense is indicated by adding "het ge-" and the future tense is indicated by adding "sal". Verbs are not otherwise changed.
Ek loop. - I am walking.
Ek het geloop. - I have walked.
Ek sal loop. - I shall walk.
Die hond eet sy kos. - The dog eats its food.
Die hond het sy kos geëet. - The dog ate its food.
Die hond sal sy kos eet. - The dog will eat its food.
Present tense: SUBJECT + VERB + OBJECT
Past tense: SUBJECT + het + OBJECT + ge-VERB
Future tense: SUBJECT + sal + OBJECT + VERB