How do i set in my x and y values...
Since you posted this in the Excel section I'll assume you're using Excel for data entry. Just create two columns, one with your X values and the other with your Y values. Select those two columns (click the column headings), then select the XYXY command of the DPlot Add-In.
You might also want to take a look at the example spreadsheet distributed with DPlot (examples.xls in the same folder where you installed dplot.exe).
...how do i get the four quadrants...
Once you have your graph in DPlot, select Options>Grid Lines or Box>Axes at 0. If you have both positive and negative X values, you'll get a dark line at X=0. The same applies to Y. Other options that might interest you here are the 3 general layout buttons on the toolbar: "No grid lines", "Grid lines", and "Box".
If your X (or Y) values do
not cross X/Y=0 but you still want to show those quadrants, you can force the extents of X and Y using Options>Extents/Intervals/Size. To get the exact extents you want you might also need to check "Specify interval" under "Tick intervals" and enter intervals that divide evenly into your extents.
...how do i join points to give a curve
That's the default for a new curve, so I'd guess you haven't got that far yet. If you try all the above and still have trouble let me know.