You use "vous" twice because "se garer" is a reflexive verb.
The first "vous" is the subject and the second "vous" is the reflexive pronoun, literally:You can park yourself here.
In French there exists a lot of reflexive verbs and some verbs which can be used either in a reflexive or a "standard" way.
-- Chris (not a native speaker).
Sign in to submit your answer
Don't have an account yet? Join today
Test your French to the CEFR standard