Virtual Population Analysis (VPA) is a widely used model for the analysis of fished populations. While there are very many VPA techniques, they vary in the way they use data and fit the model rather than in the form of the model itself. This manual describes the common VPA model and the assumptions on which it is based, together with descriptions of associated diagnostic procedures and common reference points. More importantly, the manual describes the numerical techniques which can be used to f it the model based on weighted least-squares, which is the basis for the ADAPT approach. The techniques are described so that they are readily implemented in a spreadsheet. General methods and specific examples are given to enable the readers to develop an approach suitable for their own data and fisheries.