Hello Again Helena,
Open the box and here is the "tuning card" for the instrument and you should be able to use your guitar tuner for it providing you have a key or somesuch to twist the pegs.
The instrument is tuned to a major scale usually in G ascending: G A B C D E F# G A....
It doesn't take much turning to result in large changes in pitch so go at it gently.
Hope that helps.
Happy Christmas;
Doug