Hi there, I'm a leftie mirror image knitter too! Don't panic. Mostly things work fine by simply reading the patterns as written. All that happens is your finished item comes out mirror imaged of the written pattern. So, for example, if you're knitting a cardigan, the left side turns out to be the right side and the ride side the left side and as long as you do one of each your good!
Please ignore the post above about changing decreases (sorry to the person who wrote it!). If you are following a written pattern, follow the inc/dec as written. They will slant the opposite way to a right handed person, but you are also knitting the row the opposite way so that is what you want to happen.
I suggest you continue with written patterns for now and don't try charts just yet. This is when you have to start working out which way increases/decreases go.
Please yell out for any other help.........I'm still learning too, but going in the right (or left!!!) direction. I just wish more designers recognised us lefties! The only other thing you need to watch is where the pattern refers to the left or right needle, make sure you swap this. For example, sometimes, it says something like, "leaving the stitch on the left hand needle". Read this as right hand needle and it will make sense!