It should be omitted - the comma obscures the meaning.
The phases "indicated above" and "presented below" are complete phrases in themselves and should not include a comma.
In fact, with the comma, the sentence seems incomplete, and leaves the reader expecting something like:
Place the item as indicated, above the table [or above something else].
i.e. It has previously been indicated that the item should be placed above the table.
A correct example will be presented, below the diagram [or below something else].
i.e. The example is presented below the diagram.