You might write your enumeration like this, whereby the preposition will apply equally to each word in your list, without the need for repeating it: -

To: -

1. Add...
2. Program...
3. Write...

You might write your enumeration like this, whereby the preposition will apply equally to each word in your list, without the need for repeating it: -

To: -

1. Add  ...,
2. Program  ...,
3. Write  ...,