Il y a is idiomatic meaning “There is/are”, but how do you conjugate this in to different tenses? Well, you simply conjugate avoir (a) to the relevant tense using the “Il/Elle/On” form:

Present: Il y a – There is/are.

Imperfect: Il y avait  – There were.

Passé composé: Il y a eu – There have been.

Future: Il y aura – There will be.

Conditional Present: Il y aurait – There would be.

Conditional Past: Il y aurait eu – There would have been.

Past perfect: Il y avait eu – There had been.

Future Perfect: Il y aura eu – There will have been.

Near Future: Il va y avoir – There is going to be.

Near past: Il vient d’y avoir – There has just been.