Multiple Choice type alternatives

I've read the documentaion several times, but still can't find a way to do what I need.  I was trying to use a mult-choice field so particular EVENTS records could select mutiple categories for classification.   Unfortunatley, the number of categories I need won't fit across the width of the form.  So, I turn my thoughts to using a new table (called CATEGORIES) to enter as many categories as needed and link this to the EVENTS table.  I expected to be able to select from a list of category names displayed on the EVENTS entry form.  I'm obviously going about this the wrong way, because all I get is a way to enter a new category name and no list.  Nor can I find a way to populate any other field type from a table.  Please help me.