Using Custom Columns & Measures to Sum Rows and Group by Column Values

Thanks in advance to all those that take the time to offer their help. I am new to PowerBI and I am working a project to learn new skills. I am stumped by how to represent this in PowerBI.

The context is business development. Each row in the data represents an Opportunity that has an Account Name tied to it & a revenue time series (each column represents one month). Each Account Name may have multiple Opportunities tied to it. I would like to sum all Opportunity revenue grouped by Account Name.

When I solved this problem in excel I summed each Opportunity's lifetime revenue then used SUMIFS to sum the revenue from all Opportunities grouped by Account Name. I've tried making custom measures and columns and writing in formulas but they don't seem to work.

I appreciate any and all help on how I can recreate this solution in PowerBI. At this point I'm stumped and I'm wondering if this type of solution is even possible in PowerBI.