Hello Scott,
For an existing table - create a new sequence, change the default value of the PK field, change the owner of this sequence to the PK field:
CREATE SEQUENCE "public"."sequence1"
INCREMENT 1
MINVALUE 0
START 0;
ALTER TABLE "public"."table1" ALTER COLUMN "field_pk" SET DEFAULT nextval('sequence1'::regclass);
ALTER SEQUENCE "public"."sequence1"
OWNED BY "public"."table1"."field_pk";
Each table must have its own sequence.
For a new table, it is simpler - just set Serial/Bigserial type for the primary key field.