1) Sort Data in DataSet QueryYou can sort the data in your query that you are using for DataSet definition. Let's say we would like to sort the data by Region, we can use below query in our DataSet. If you are using Stored Procedure you can use Order by clause in your Select query inside Stored Procedure.
2) Sorting Data with ExpressionsYou can sort the data in report after retrieved from data source. You can enabling sorting on Tablix,group or detail group. Sorting can be enable on Tablix, Matrix,List, Chart,Gauge etc. Click the properties of Report Item and if you see Sorting listed in properties you can enable sorting on those report items.
Here is example how you can enable sorting on tablix