Does this sound alright with a modifier in the sentence. Standing on a ladder,I was just able to reach the high window.

Yes. You've got it.

The participial phrase, "standing on a ladder," modifies "I."

Yes, the sentence "Standing on a ladder, I was just able to reach the high window" is grammatically correct with a modifier. In this case, the modifier "Standing on a ladder" is a participial phrase that provides additional information about the subject "I" and describes the action taking place.

To identify and use modifiers correctly in a sentence, you can follow these steps:

1. Identify the main subject and verb in the sentence. In this case, the subject is "I" and the verb is "was able to reach."
2. Decide what additional information you want to include in the sentence to modify the subject or the verb.
3. Construct a modifier using an appropriate word or phrase. In this example, the modifier "Standing on a ladder" describes the subject "I" and provides information about the action being performed.
4. Place the modifier in a logical and grammatically correct position in the sentence. In this case, the modifier is placed at the beginning of the sentence, separated by a comma.

By following these steps, you can effectively use modifiers to add descriptive details and clarify the meaning of your sentences.