past tense
If they are events that "happened" then you need to use the past tense.
present
When writing about literature, the past tense is typically used to discuss events or actions that have already occurred in the text.
Use present tense when describing actions, events, or states that are currently happening or are generally true. Use past tense when discussing actions, events, or states that have already occurred or are no longer true in the present.
Describing how to do a process is usually in the present tense.
To express/talk about events that are going to happen in the future.
The past tense is used to describe actions that have already happened, while the future tense is used to talk about actions that have not yet occurred but are expected to happen in the future. Use the past tense for events that have been completed, and the future tense for events that will take place.
when you want to signal a change in time
The simple future tense is used to refer to something that has not yet happened but will happen in the future.
there is no past or future tense. it is an adjective/describing
Happened is the past tense of happen.
The past tense of happen is happened.