Hola Celia

The conjugation of acabar de is that of an regular -ar verb in any tense. We haven't mentioned anything related to conjugation in the lesson as it is an idiomatic lesson. The examples you see in the lesson are mixed, some in the present (acabo de) and some in the imperfect (acababa de). These are the tenses normally used in this construction. So if you want to say "someone has just done something" you conjugate acabar in the present:

If you want to say "someone had just done something" then you conjugate acabar in the imperfect:

We will add a note to the lesson to make it a bit more clear.

Gracias y saludos

Inma

Hola William

The examples used in lessons that are purely conjugation ones have lots of different verbs in the sentences and possibly different tenses, so it'd be impossible to include all the links to the different cases that you find in a specific non-conjugation lesson for all different verbs and different tenses. 

If there is a particular verb you'd like to know about in terms of conjugation, you can search it up in the library by typing for example "traer", "estar", "hacer", i.e. the infinitive of the verb you want, and if we have lessons on those specific verbs they'll come up with the titles. All the conjugation lessons start with "Conjugate ..." so they will be easy to spot. 

If you don't find any lesson on a verb that you type, that will be because we will have that verb in a lesson where we explain about a set of regular verbs, or a certain irregularity so the title won't contain that verb in particular. If you struggle to find anything you can always use the forum and we will guide you through it or give you the direct link to that topic. 

I hope it helps.

Saludos

Inma