Question

The sun shine brightly is a simple present tense

Answer 1

The sun shines brightly.

The form of the tense is simple present tense. So if you wish to convert the sentence to this form, no conversion will actually be needed due to it already being in this form.

Here are examples of the same sentence in simple past tense and the simple future tense:

Simple past tense: The sun shined brightly.

Simple future tense: The sun will shine brightly.