Excel can be a bit non-intuitive when it comes to charts. Assuming that the sheet is Sheet1, the X axis values are in A1:A20 and the Y axis values are in B1:B20 then
Select B1:B20 and use the Chart Wizard to create a bar graph. Then right click one of the bars and select Source data. On the Series tab > Category (X) axis labels enter
and click OK.
You can then right click the X axis, select Format axis and adjust the decimal places etc. as required.