In the current version of the SimBiology Desktop, experimental and simulation data cannot be viewed together in the plots generated after a running a simulation, but they can be viewed together in the Live Plots. Assuming you have already created a model and simulation task, and have also imported your experimental data into the SimBiology desktop:
1) With your simulation task open, click on the "Live Plots" button in the "Editor" tab of the toolstrip.
2) Switch to the "Explorer" toolstrip tab and click on "Edit Properties" to bring up a window for configuring your live plot.
3) At the top of the "Data to Plot" tab of the "Properties" pop-up window, there is a drop down menu that allows you to choose between State, External and Math data. Choose "Plot External Data" and click "Add". A new row for your experimental data will appear in the table of plotted variables.
4) Select this row and configure the X column name, Y column name, etc.
5) You can repeat this for any number of states, external data columns or also arbitrary math lines.