You can use the two icons 
Series in columns and 
Series in rows on the contextual ribbon tab Chart | group Data to determine whether the data to be displayed should be evaluated column by column or row by row:
▪By columns
| The first icon is selected by default, thus the data will be evaluated column by column. The values in the first column will be the first data series, the values in the second column will be the second data series, etc. |
▪By rows
| If you click on the second icon, the data will be evaluated row by row. The assignment of the rows/columns in the worksheet to the X axis/Y axis in the chart is thus reversed. |
Alternatively, you will also find this setting in the dialog box of the ribbon tab Chart | group Data (click on the group arrow
) and switch to the Data source tab.