if you want disable only trailing_whitespace then, 
- launch Terminalapp and move to your project folder.
- execute the command $ ls -ato see all the hidden files. you will see there is .swiftlint.yml file
- open the file in your editor. $ vi .swiftlint.yml(if you installed Sublime Text in your mac, then use this;$ subl .swiftlint.yml)
Lastly, add trailing_whitespace in disabled_rules.
disabled_rules: # rule identifiers to exclude from running
  # - colon
  - comma
  # - control_statement
  - variable_name
  - force_cast
  - large_tuple
  - notification_center_detachment
  - nesting
  - function_parameter_count
  - trailing_whitespace # <---------
opt_in_rules: # some rules are only opt-in
  - empty_count
...
However, I recommend to use autocorrect rather than adding trailing_whitespace in the setting.