Click on the checkboxes in the Data column on the Data and Parameters tab to select/deselect the data series to fit to for each model Scenario. 

Multiple data series can be selected.  The data can be visualized and individual or groups of data points (e.g. outliers) can be de-selected in the View Data window.

Only data series in the Scenarios you have selected will be used for fitting.

All data series in all scenarios can be selected using the check box at the top of the panel.

As a general approximation, one data series containing at least four data points that captures a profile shape will be required for each parameter that you intend to fit. This guideline will help to avoid local or 'false' minima that may lead to an erroneous kinetic model.  If you cannot fit your data with this approach, modestly increase the number of fitted parameters, guided preferably by mechanistic insight into the process under consideration. 

The above guideline does not prevent you from developing a reaction scheme that is chemically realistic and useful with fewer data.  However you may need to fix high values for certain rate constants in your scheme based on intuition or hints contained in your data (e.g. for acid-base reactions). You can then focus on getting a good fit for the rate-determining step(s) in your system based on available data.