When fixing the refrigerator, consult the user manual.

Literal

Refrigerator [object-を] fix [if-なら] instruction-manual [object-を] consult [imperative].

~なら is the conditional marking 'if (it's the case that).' 取扱い説明書 is a compound of 取扱い ('handling, use') + 説明書 ('explanation document') = 'user's manual.' 参考にする ('use as reference, consult') is a set phrase.