There are lots of ways to convert your barrel into a usable rain barrel, but these instructions will show you the simplest way to do it. This method only requires drilling two holes (one if you use a utility knife), and it doesn't require cutting a huge hole in your barrel.
Step 1: Parts List
Food Grade Barrel
1" ID (Inner Diameter) Hose
3/4" Drill Bit (optional, Utility Knife can be used instead)
1" Drill Bit
Nylon 3/4" MIP to 1" Barb Adapter
3/4" Hose Bib
Rain Water Diverter (can be bought or made. It is important that the diverter handles overflow when the barrel fills up)
Barrel - $20.00
Hose - $5.76
Adapter - $2.71
Hose Bib - $4.94
Total - $33.41
The diverter can easily cost as much as the rest of the system if it is bought online.