。
Help me out with cooking.
Literal
Cooking [object-を] do [nominalizer-の] help [informative-よ].
手伝う ('to help, assist') takes the nominalized verbal phrase ~するの as its object. The の is a casual nominalizer, common in spoken Japanese for turning a verb phrase into a noun-equivalent. The sentence is a direct casual request. よ for informative/friendly insistence.