"还有" (háiyǒu) is used to express "In addition..." in a conversation. It is introducing new information to the topic the speaker(s) is/are talking about. While it's not the most challenging grammar structure, an important thing to keep in mind is that 还有 starts a completely new sentence or clause.

Structure

It's as simple as using 还有 before the new clause or sentence. 还有 can also be used with a comma, similar to how we can say "in addition, . . ." in English.
Clause 1 ， 还有 + (，)+ Clause 2

Examples

Nǐ xūyào chī diǎn yào. Háiyǒu, yào duō xiūxi.
你 需要 吃 点 药。还有，要 多 休息。
You need to take some medicine and get more rest.

Wǒ jīntiān yào kǎoshì. Háiyǒu, wǒ bìxū yào xiě wán zhōnɡwén zuòwén.
我 今天 要 考试。还有 ，我 必须 要 写 完 中文 作文。
Oh, man! I’m going to have a exam today and I have to finish writing my Chinese essay.

Jīntiān tèbié dǎoméi, tāde nǚpénɡyou líkāi le tā, háiyǒu tā de láobǎn yào jiěɡù tā.
今天 特别 倒霉，他的 女朋友 离开 了 他，还有 他 的 老板 要 解雇 他。
Today it's really unlucky. His girlfriend left him and on top of that, his boss is going to fire him.