I don't know what SVM is, but you need a set of situations for which you know the correct classification (a 'gold standard') and then just compare your classificator with the gold standard. TN = number of events that are negative that your classificator classified as negative, FP = events that are negative but that your classificator classified as positive, TP = events that are positive that you classified as positive and FN = events that are positive but that you classified as negative.
SVM stands for support vector machine. There are several matlab implementations for that, so I cant give you a clear answer. But I participated in similar questions. If you don't find your answer there, please ask a little bit more elaborate.
This paper introduces a detailed explanation with numerical examples many classification assessment methods or classification measures such as:
Accuracy, sensitivity, specificity, ROC curve, Precision-Recall curve, AUC score and many other metrics. In this paper, many details about the ROC curve, PR curve, and Detection Error Trade-off (DET) curve. Moreover, many details about some measures which are suitable for imbalanced data are explained.