If something is made of or made out of a particular substance, that substance was used to build it.
The top of the table is made of glass.
该桌台面由玻璃制成。
Made is the past tense and past participle of make.
have it made
If you say that someone has it made or has got it made, you mean that they are certain to be rich or successful.
When I was at school, I thought I had it made.
上学的时候,我觉得自己一定会有所作为。