Your speed settings are found at LW's menu bar, Tools -> Options -> Advanced -> Transfers, you will see options for setting your speed to either Broadband or Dial up at bottom right of window. At top of window you will see options for limiting either upload/download speeds. If you wish them to be unlimited do not limit them.

Are you referring to uploading to other people, or speeds of downloads? For download speeds, re-searching for file & using the Get More Results by right-clicking search tab to find more sources to download from can help.