The current user must be the owner of the database function or have the DROPIN privilege for the schema to which the database function is assigned.
More information: SQL Reference Manual, Privilege Specification for a Schema (schema_priv_spec)
The database is in the ONLINE operational state.
In the explorer tree, open the Functions folder.
In the context menu of the database function, choose Delete.
SQL Reference Manual, DROP FUNCTION Statement (drop_function_statement)