Task: In the RAR app , Compress the file download in RAR format at Fast compression level and 64 MB dictionary .
Steps:
Open the RAR app
Click on the check box of the download floder
Click on the compression button at the top of the screen
Click on the Advanced option
Click on the Compression level drop down button
Choose Fast compression from the options
Go to the dictionary level selection 
Select the 64 MB dictionary 
Click on the OK button at the bottom right corner of the screen