wont let me download apps! Help!!

Hi all, I got a iphone today off a friend, Had been reset to factory settings, Ive done a apple ID and set the phone up, Now i want to download apps like whats app, Snapchat etc but when i select 'Get' it asks for my itunes store password, So I enter that and it doesnt download, so I'll select 'Get' again and nothing happens. Sometimes it will say cant connect, But im connected to my wifi. once its been stuck on waiting for ages not doing anything. what can I do to fix this?