Export data table to Postgres

When I try to upload a data table (from CSV) to a newly created Postgres table with the command "write to table in schema public in PostgreSQL database cmdb..." and mark "Modify destination table to fit data", the process stops with "This table does not have a primary key, which is required in order to be able to identify individual rows."
How can I then upload a data table to a new database table in PostgreSQL. Additionally , I've not found something where I can declare a column in a CSV table to be "unique" or "primary".