How was the bill of rights added to the constitution?
As 10 new amendments
It was added as a compromise between those that supported ratification of the Constitution, called Federalists, and those that were opposed to ratification, called Anti-federalists. Anti-federalists agreed to support ratification of the Constitution if the Bill of Rights was added later, which is why the Bill of Rights is the first 10 amendments to the Constitution.
A bill of rights was not included in the Constitution because most of those who wrote it did not think one was needed. What we now call the Bill of Rights was added as the first ten amendments to the constitution because the States would not ratify the Constitution without a promise that such a Bill would be added.
Some states or people (like Virginia's Patrick Henry) thought that the Constitution did not adequately protect individual citizens' rights. Therefore, a Bill of Rights was added so more states would ratify the Constitution, and the American people were afforded more protection than with the Constitution alone. The Bill of Rights added a significant number of rights and privileges not given to citizens under the Constitution alone.