The past tense is when you write or speak about something that happened in the past or before present (now). So if you were to say I WENT to the shop, the WENT indicates that it happened before now however if you said i am going to the shop, am going indicates that it is happening now which is the present tense.
The past tense of "explain" would be "explained".
the past tense of am is was and the past tense of has is had
The past tense of "has" is "had" and the past tense of "have" is "had."
Was and were are both the past tense of be. The present tense is: I am he is you are they are The past tense is: I was he was you were they were
"will be" is the future tense of "be". The past tense of "be" is "was/were".
The past tense of "she do" is "she did."
The word "were" is past tense. It is the past tense of the verb "to be."
The past tense of "will" is "would" and the past tense of "be" is "was" or "were" depending on the subject (singular or plural).
HAD is the Past Tense of TO HAVE.
The past tense of "am" is "was" and the past perfect tense of "has" is "had."
The past tense of "have" is "had."
The past tense of "you will not" is "you would not."
The past tense of "exist" is "existed." The past perfect tense is "had existed."