I don't use phpPgAmin.
To change an existing column definition to use the
CYCLE attribute you need to understand that this is an attribute of the sequence not the "column".
bigserial is only a shorthand notation to assign a default value to a column which is take from a sequence.
When you define a column as
serial Postgres automatically creates a sequences and applies the necessary default expression.
The sequence is usually called
<table_name>_<column_name>_seq. But you can run a query to get the name of the generated sequence:
select pg_get_serial_sequence('your_table_name', 'your_column_name');
Once you know the name of the sequence, you can do the following:
alter sequence your_sequence_name cycle;
(Note that you need to
commit that if you are not using auto-commit mode).
Here are some relevant links to the manual: