Before starting any fit, one must import phases, link them to histograms, ensure that lattice parameters are sufficiently close that refinement will progress, set up a background model, etc. The steps needed here have been discussed in the chapters in III. At a minimum, you will want to place some special attention onto the refinement of the first dataset in a sequential fit. As noted, you may want to do this with several different histograms across the series of measurements. How this will be done is also a personal style. In the tutorial, a GSAS-II project is created with a single histogram and two phases. This refinement is performed as a standard combined fit and after that is done, additional histograms are added and the refinement is set to be a sequential fit. It is also possible to start that fit by importing the entire sequence of datasets and then to initially select a sequential fit for just the first dataset until you are ready to progress to a fit of all datasets.