First you'll have to run over to mirc.net and go into the addons section, find the addon XDCC browser, dont worry its easy to find. Download it and extract it into a new folder in your mirc directory.
Pop open mirc and type in: /load -rs c:\progra~1\mirc\yourfolder\xdccb.mrc
follow the prompts, then join your favorite xdcc/fileserver channel and let it make it a point and click process.
Note: in the config some bots dont reply to /ctcp, ya might need to change it to /msg to get it to work, and if ya close the xdcc browser window, ya can always right click in the window to reopen it.