In Latin, as in other languages, the verb has two voices: active and passive. For crating the passive voice, Latin language  uses two different systems: one for the present tense, and another for the perfect tense.

PASSIVE VOICE IN PRESENT TENSE:

To form the passive voice of present tense, both for the indicative and the subjunctive, personal endings of the passive voice must be used. It is simple, you should change the active voice endings for the passive voice endings:

PASSIVE VOICE IN PERFECT TENSE:

It is formed with the perfect participle of the verb conjugated + SUM in the corresponding tense (present or perfect):

TIEMPOS DE PERFECTO DE LA
VOZ PASIVA

The matching rules are the same that we use with nouns / verbs and adjectives / subjects, a verb form such as DICTUS EST will have singular masculine subject.

PASSIVE SENTENCES:

In the sentence “The girl loves the Queen” (expressed in the active voice) we have a subject (the girl), a transitive verb (loves) and a direct object (the Queen). This idea can be expressed in the passive voice: “The Queen is loved by the girl”. In the second sentence we find the following: a patient subject (the queen), an agent subject, that performs the action (by the girl), and the verb in the passive voice (is loved):

Puella reginam amat > A puella regina amatur

In Latin, the patient subject is in nominative, the verb, in passive voice, coincides with the patient subject and the agent subject is in ablative case (with a or ab prepositions if it is a person or a personified thing, and in ablative without a preposition when it comes to a name of a thing). It is called agent ablative: