How can I "flatten" a table for analytics

Greetings.

I am new to PowerBI, and in Data Analysis for that matter, and have in my hands an expenses table, with relevant data in both columns and rows, similar to this:

And I need, inside PowerBI, to flatten it so each entry has a supplier, CC, month and year, as such:

I need to reorder it so I can build a dash, showing how much was spent through the year and allowing filters by Supplier and/or CC. I thought of simply making new tables, for months, years, CC and Suppliers and sums from the source data then creating relations between them but am finding difficulties since I have zero training on the software.

Any help is much appreciated.