Here are some examples so you use tenses correctly. Notice the previous post has a verb list and therefore, you can look at the verb and tense you want to use.

what I normally do:

Nosotros vamos a conciertos 1 vez al año/ Nunca leo sobre arte/ My mama trabaja en su casa. 

 We go to concerts one time a year / I never read about arts / My mom works at home

When I want to talk about a particular occasion.

En esa oportunidad yo fui al campo/  Nosotros estábamos cansados ese día/ Comió el pastel y se fue.

I went to the country on that occasion /We were tired that day/ She/He ate the cake and left.

About things that started in the past and continue to the present...

He estado bien cansada ultimamente/ No he comprado tantos dulces / He querido ir pero no he podido

I have been tired lately/ I have not (haven't) bought many sweets/ I have wanted to go but haven't been able to.

When I am talking about the past and I want to refer to something further in the past.

Ese día me di cuenta que lo había visto más temprano. / Hasta entonces no había tenido tiempo.

That day I realized I had seen him earlier./ I hadn't had time until then.

Conditionals

Si tengo tiempo, te llamare.

If I have time, I will call you.

Si tuviera tiempo, te llamaría.

If I had time, I would call you.

Si hubiera tenido tiempo, te hubiera llamado

If I had had time, I would have called you.

Modals
Creo que puedo ayudarte/ Tú deberías trabajar un poco más / Ellos irían si  ella  los invitara

I think I can help you /  You should work a little more (harder) / They would go if she invited them

I hope this helps :)