According to the declaration of independence when should the people have the right to change their government

Not necessarily according to the Declaration of Independence. Ye must understand that the Declaration is siting the God-given right, under Natural Law. 
The document simply states that these rights exist, but it also states that it is according to God that these rights are endowed in all men equally. 

When government becomes abusive to its people, it is the right of the governed to alter or abolish it.