一个英语小语法

楼主理解有点偏差，本句不是定语从句，而是宾语从句，主句是：She visited people's homes to show; 从句是：how home care products such as cleaning fluids and equipment helped ease house work. [其中home care products做宾语从句的主语，such as cleaning fluids and equipment作插入语，helped ease house work作宾语从句的谓语。]所以，宾语从句可简化为：how home care products helped ease house work，应该看清楚了吧，这里helped ease house work 并不是作定语，而是作谓语。
说到这里，整句的意思就不难理解了：
She visited people's homes to show how home care products such as cleaning fluids and equipment helped ease housework.
她拜访人们的家是为了展示比如清洗液或设备之类的家用产品是怎样帮助减轻家务劳动的。

show 后面跟的是个how引导的宾语从句，既然是从句，肯定要有时态。

我同意wzh868的看法

how home care products such as cleaning fluids and equipment helped ease house work是show的宾语。
现在先不管主句，只看这个陈述语序的从句home care products such as cleaning fluids and equipment helped ease house work。其主语是home care products,谓语是helped。这里hleped为什么会用过去时态呢？这个时候我们就要看主句了，主句的谓语是visited，用的是过去时态，因此，为保持整句的时态一致，这个从句的谓语动词也应该用过去时态，即使从句的动作是发生在现在也要跟随主句的时态走。
不知道我讲明白了没。

how