shicked is a term used to describe when you are so shocked that you soil oneself.

A term used to reference cannabis/marijuana/weed.

A cross between being shit and fucked.

<interjection> Chiefly Anglo-Scottish Slang;
Used to express a sexual attraction to another person.

--> The term is abnormal; There is no definite rule to using the word. Although, being an interjection, a rule of thumb would be to use it in the same way as "Wow." It is kind of the same as saying, "Hey, I want to shag you!" only in a single word.
As with most slang, the only way you can use it is how you feel it should be used...

When someone is so shocked that they shit a brick

A phrase to substitute for having the shit kicked out of oneself or another.

To be promised something only to get proverbially fucked in the ass.