Creating brand new word entries
Skritter has hundreds of thousands of word entries and it's likely that what you're searching for already exists. However if there is something that you want to add that isn't in the database yet, you can easily create your own custom entry.
How to create a new entry
When you attempt to add something that doesn't exist in the database yet, you have the option to create a new entry.
After clicking the "Add Entry" button, there is a dialog to enter the pinyin reading and definition for the new word. Once you've filled this out, you can add the word by tapping the "Add Word" button.