WinRAR the volume compression file method.
First, choose the file you want to compress, click the right mouse button to select "Add to Compressed file".
Then, in the lower left corner of the compression method to choose the "best", the following figure, then, in the lower left corner of the compression volume to select the compressed volume size, or set the size of your own individual volume file, fill the size of the unit, the general use of "KB." Finally, point OK, start compressing!
Note: If you want to compress the file has a large number of small files, select the right side of the "Create solid compression file", the effect will be better, will be all small files as a whole document to treat, effectively save space.