Hi,
'Vill' means 'want' e.g. 'jag vill' (I want), 'du vill' (you want) etc.
In your example above, 'Var vill du äta någonstans?', the words 'var' and 'någonstans' should be considered together as the word 'någonstans' reinforces the word 'var'. You could actually rearrange that sentence to 'Var någonstans vill du äta?' and it would make no difference in meaning.
'Någonstans' by itself means 'somewhere'.
'Where are your keys? Here, somewhere'
'Var är dina nycklar? Här, någonstans'