Many things in life can be difficult for the left-handed person, and that can include handcrafting things like knitting wool. It's not because the needles are designed for right-handed people or anything like that, but nearly all the instructional videos and tutorials show how to hold the yarn and needled from a right-handed approach.
So really, the problem comes with the learning aspect of knitting not the actual doing of it. Once you've learned how to work the stitches as a lefty, there is no problems whatsoever in knitting left-handed.
One approach is to simply learn a right-handed method and practice until you get it. Knitting does take two hands, so everyone who knits is using their less-dominant hand in some way. You just need to master how to work the stitches using your right hand. It might seem awkward at first, but it can be doable. Taking this route means you can eventually utilize any tutorial or pattern you find, since they are almost always written for right-handed people.
Alternatively, you can knit "backward", so that your stitches are worked from the right needle over to the left one. This is probably the easiest in terms of your own comfort because you are using your dominant hand for most of the work. But it will be harder to follow any instructions. You have to reverse references to left and right for all written tutorials.
For example, here is how you would do a basic knit stitch, left-handed:
Hold your yarn in the left hand, over your index finger and held with the others for tension. Slip your left needle through the first stitch on the right-hand needle (from front to back). Yarn over the left needle and pull it through to make a new stitch now on your left-hand needle.
And here is how you do a basic purl stitch, left-handed:
Again, hold your yarn in your left hand, with tension over your index finger. Keep the strand of yarn in front of your needles, and slip the left-hand needle through the first stitch (from back to front). Yarn over the needle, wrapping from back to front, and pull back through for the new stitch.
You may need some more graphic assistance to really visualize the left-handed method, but the point is that you can easily describe either basic stitch in reverse when you need to.
As the era of online video tutorials grows, more and more left-handing knitting resources can be found. If you are technically inclined, there are several video editors that will allow you to mirror-flip a video, which can help you see how the stitches work in a left-handed viewpoint.
One final option for south-paw knitters is to use the Continental knitting method. This is already a left-handed technique and any patterns or instructions for it will be appropriate for you without any adjustments. There are plenty of good tutorials and videos online for this style, which can be a good entry point for easy left-handed knitting.
Really, you can take several approaches to master knitting left-handed and start to create your own yarn masterpieces.