Go to "Tools/History Center" or hit F2 on your keyboard. A box will pop up titled "History Center" In the left side of the window you will see a list of all the currency pairs that your broker offers. Different brokers organize these differently, some brokers will divide the currency pairs is sub folders, while others will simply list then all in a row. Find the GBPCHF pair and select it. At the bottom left hand side of the window, click the "Download" button. A warning about MetaQuotes data may pop up, click ok. The chart data may take several minutes to download. Once the data is finished downloading close the "History Center" window, then restart MT4. Once you have finished, the GBPCHF chart data has been properly downloaded for back testing. You will first need to do this for any pair that you wish to properly back test. ( you do not need to restart MT4 every time )