Open a command line instance in the bot's directory and run ./discord-set-slowmode-bot, a warning should be printed client id is not specified, check cfg.yaml file and cfg.yaml will be created.
Copy your bot token into cfg.yaml replacing <your-bot-token-here>.
Run ./discord-set-slowmode-bot again, once connected, copy the discord invite link to your favourite browser and add the bot to a server. The bot should now be present in the desired server.
In discord, from the channel you would like to set slowmode, type @SlowModeBot <duration> e.g. @SlowModeBot#8558 1s for 1 second, @SlowModeBot#8558 2m for 2 minutes or @SlowModeBot#8558 2h for 2 hours.