I would first use ImportMatrix to import the data (this is more general than the ExcelTools option and will also handle Excel files).
MyData := ImportMatrix("PathToMyData")
Now that you have the data, use the TimeSeries command to turn it into a Time Series object:
MyTS := TimeSeries( MyData, headers = 1, dates = 1)
Since you mentioned that the first column is a column of dates, we need to add the 'dates' = column number as an option such that the time series is created using your dates. Similarly adding 'headers' = 1 specifies the names of the data sets contained in the TimeSeries, in your case, this is month names.
Some TimeSeries commands will only work on one dataset of the TimeSeries at a time, so you might need to specify which column (or dataset) to work with. To plot it for example:
TimeSeriesPlot( MyTS[..,1] ) would plot 'January'.
TimeSeriesPlot( MyTS ) would also work if you wanted to plot all months.
There is a good example which runs through all of these steps on the Time Series - what's new for Maple 18 page.
Hope that helps!