If you have a table name with spaces in it, the Add Entity action reports "Could not process Table 'xxx' Make sure you have SELECT Rights on the Table/VIEW" when you try to add it.

I found this in MS Access, but it may be a general issue.

As a work around, I created a copy of the table, edited the table name to omit the spaces, and added with the Definition Editor. I then exported the XML and hand edited the table name in the SQL statements from TableNameWithSpaces to "Table Name With Spaces". You can also rename the table display name to Table Name With Spaces (no quotes) and the table name will display correctly in the Definition Editor.