I don't know what vosotros is and how it fits in with the other forms. Is there a lesson to help with this please?

Hola Dave

Vosotros is the pronoun that refers to a "you plural" (informal, when you are talking to a group of friends or people that you know, young people... as opposed to the other formal you plural: ustedes, which is used formally)

It is a pronoun that is used in Spain, not so much in Latin American Spanish, where they always use "ustedes". 

In Spanish nosotros has a specific conjugation with a specific ending for each tense.

Kwiziq content is based on Spanish from Spain at the moment, until we can extend it with specific lessons for Latin American Spanish. 

Un saludo cordial

Inma