Hi friends. How r u? I observe some people are so worried about TENSE. In fact tense is very important though learning TENSE is not at all difficult. Let's discuss how we can learn TENSE with little care. Observe the following carefully: (Let's see what happens with the verb DO in different tenses.)
Tense         Simple              Continuous             Perfect             Perfect Continuous
Present         do               am/are/is doing    have/has done     have/has been doing
Past             did               was/were doing      had       done              had been doing
Future  shall do               shall be    doing    shall have done           !!!!!!!!!
             will  do                will be   doing       will have done  

From the above you can well understand that continuous tenses have the +ing form and perfect tenses have the past participle form of the MV (Main Verb). And what about the Past simple? The MV changes only into its past form.
And now when shall we use which TENSE?  Just imagine you are standing right here and it's PRESENT. Your back is PAST and your front is FUTURE. The action running is continuous and the action finished is perfect. The action that started some time in the past and still continuing is Perfect continuous. Note the HVs (Helping Verbs) carefully. In continuous, perfect and perfect continuous tenses the MVs remain unchanged but only the HVs change.
Here are some examples. Read them carefully.
I was in class VII last year.  ----- Past Simple
I am in class VIII this year.  ----- Present Simple
I shall be in class IX next year. -- Future Simple
The fan was moving yesterday. ---- Past Continuous
The fan is moving today.  ----------- Present Continuous
The fan will be moving tomorrow.--Future Continuous.
That's all for now friends. We hope to discuss Perfect tenses next time because they are a bit difficult. Feel free to ask questions. Good night and sweet dreams.