Сделайте очень надо past simple past past progressive past perfect 

Present simple present progressive present perfect future simple  а вот само предложение 

I write the letter to my pen friend

I often write the letters to my pen friend.  (Present Simple)

I am writing the letter to my pen friend now. (Present Progressive)

I have already written the letter to my pen friend. (Present Perfect)

I shall (will)  write the letter to my pen friend tomorrow. (Future Simple )