We must be able to speak it ourselves correctly. 
这个句子中 ourselves 是主语补足语，还是反身代词作状语，相当于 by ourselves，只是省略了by？自己搞不懂了，麻烦大家给看看！

回答如下：

首先，同意唐老师解答观点，下面我还补充一些内容如下：

以上反身代词作主语的同位语，相当于下面句子

We ourselves must be able to speak it correctly.

关于反身代词作句子成分归纳如下

【1】用作同位语(加强被修饰词的语气，紧放在被修饰名词后, 或句末)

 A:作主语的同位语 :反身代词作主语的同位语时，可以放在主语之后，也可以放在句子的末尾。如： 

I myself can do it．

＝I can do it myself．

我自己能做这件事。 

Edison built a laboratory himself．

＝Edison himself built a laboratory．

爱迪生自己建了个实验室

The box itself is not so heavy.

箱子本身并不重。

Martin himself attended the sick man.

马丁亲自照顾病人。

 Don’t trouble to come over yourself.

你不必费神亲自来了。

 You yourself said so. / You said so yourself.

你自己是这样说的。

 Never leave to others what you ought to do yourself.

不要把自己该做的事留给别人做。

B:作宾语的同位语 :作宾语的同位语时，反身代词只能放在宾语之后。

I want to see the scientist himself．

我想见见那位科学家本人。

【2】 用作宾语(动词或介词的宾语)：

 Take good care of yourself. 

照顾好自己。

 He has a right to decide for himself.

他有权为自己做出决定。

He made no complaint for himself.

他没为自己抱怨什么。

She finally gained control of herself.

最后她控制住了自己。 

She could not make herself understood.

她不能使别人听懂她的话。 

Everybody here has the influenza including myself.

包括我在内所有人都患上流感。

The child cried himself to sleep. 

孩子哭着哭着睡着了。

She convinced herself that it was so. 

她说服自己情况是这样的。

He had a couple of revolvers with which to defend himself.

他只有一两把手枪用来自卫。 

【3】用作表语有时：用于 be, feel, seem, look 等后作表语表示身体或精神处于正常状态：

The poor boy was myself.

那个可怜的孩子就是我自己。

The ones who really want it are ourselves.

真正想要它的是我们自己。

I’m not quite myself these days.

我近来身体不大舒服。 

I’ll be myself again in no time.

 我过一会儿就会好的。

【4】用作主语。在现代英语中，反身代词一般不能独立用作主语，但是它却可以借助 and, or, nor 等连词与其他名词一起构成并列主语(且位于并列主语的后部)，以及用于某些特殊结构(如as...as等)：

My brother and myself went there yesterday.

昨天我兄弟和我一起去了那儿。

Jim’s sister and himself get up at six every day.

吉姆的妹妹和他每天6点起床。

He was as anxious as myself. 他和我一样担心。

【5】用于一些简短的会话用语或固定说法中。

Help yourself! 

请随便吃吧！/请自己去取吧!

Make yourself at home!

别客气！

Don’t upset yourself! 

别自寻烦恼！

Make yourself heard /understood. 

使你的话被人听得见/理解