Select menu item File and press sub-menu item Load existing dataset. Select the tutorial file “eeglab_data.set” distributed with the toolbox and located in the “sample_data” folder of EEGLAB. Then press Open.
The most common use for Tools → Change sampling rate is to reduce the sampling rate to save memory and disk storage. A pop_resample.m window pops up, asking for the new sampling rate. The function uses MATLAB resample.m (in the Signal Processing toolbox– if you do not have this toolbox, it will use the slow MATLAB function griddata).
You do not need to change the sampling rate for processing the tutorial data since it is already at an acceptable sampling rate.
Before resampling, a low-pass filter at half the resampling frequency (so 64 Hz if you resample at 128 Hz) is applied to the data to avoid aliasing effects.