I have a field that I have set to be unique. I no longer want it to have to be unique. How do I change it?

If you view the structure of the table you should see (below the list of columns) a heading saying Indexes. Below this you should see the column in question and you just need to drop the column from the indexing list (if you still want to index on the column but without it being unique you will need to set indexing on the column again).

 

Hope that helps.