If you have a SpecMol resource open in the SpecMol editor, you can assign the peaks automatically via an NMRShiftDB prediction. This works as follows: A prediction for the molecule is done, for each peak in the predicted spectrum the next match in the original spectrum is found and this peak is then assigned to the atom for wich the match was predicted.
The function is available via the menu "SpecMol"->"Assign by Prediction". You need to choose a server (default should be ok) and the nucleus, if your spectrum does not contain one. The assignment is then done and shonw in the editor. Note that you need to save the resource in order to save the assignment.