Dear Baber,
Thank you for your response.
We have an import format available for XML file camt054. Please import this and open it in designer to see how it is built.
That said you need to create your own format since the one available accepts XML format. Place your cursor on the Payment model click Create configuration:

Flag that it supports import format and click create configuration.
Then start designing the format adding File, sequence and elements just like the bank format is:

Then select map format to model since the mapping is not here, this is an import format:

Start using camt054 definition, click on Add

Then open in designer and "tell" the application what info you read from the text file to insert into the database. For example I read the vendor name from the text file and want to populate the vendor name:

With the import format you just read the file and say where it should be populated. Then you need to derive the payment model mapping to destination ISO20022 and add new rules or modify existing ones if needed. For example if Vendor name is blank then you cannot insert a

Then open in designer this definition Register processed payments ISO20022 CTCopy

Please note that I have not tried this yet, never tested but the steps are these ones.
Give it a try and then let me know how it goes.