The input to Surfer is an x, y, z file, where x is the coordinate in x direction, y is the coordinate at y direction and z is the elevation. Note that this map is done directly from your x,y,z file. It will open a dialog box. List your directory, and choose xyz .txt file and open in Surfer. Now you are ready to interpolate the data.
Interpolation is the most important part of the elevation modeling process.
You can choose from different interpolation methods and you can also adjust some variables to influence the interpolation. Some interpolation methods are good for data which have a lot of data points and the region is sampled homogeneously. It takes a lot of experience to determine what kind of interpolation method to use for particular problem. Use an appropriate number of pixels in both directions in the interpolation dialog box called Spacing . And, assign the name of the grid you are going to compute.