I can read your question 2 ways;
A) you data looks like this
x y
5 10
8 15
etc.
Select the data and make an XY chart
B) you have two sets of data
x1 y1
5 10
10 12
17 15
21 20
and
x2 y2
3 8
7 14
12 19
18 24
Make an XY chart of the first data series
Select all the data (including headers) for second set, and use Copy
Click the chart to activate it
Use Edit | Paste Special .... indicate New Series with x-values in first
column; press OK
The chart now has both data series
best wishes