i honestly thought that ppm meters where more for hydro setups and not really for soil.. but i guess they could be used for either... what a ppm meter will tell you is how much nutes are in your solution.. i am not sure about the one you have as i have never used one... but i think that you mix your nutes according to directions, then test the ppm of them... usually, seedlings and the like start off with a much small ppm, and as the plants grow, you increase you ppm... i think like seedlings start of at like 50-150ppm... and like i said, as they get bigger you increase the ppm to like 1500, strain dependent of course.. and as flowering stage progresses, you will want to start to drop the ppm back down again and eventually end up just using straight water to flush the plants with..
i am sure that there are plenty of websites that will tell you what ppm to use and when to increase/ decrease it...
in soil, i would think that you should keep an eye more on ph that ppm... if you don't already have one, get yourself a nice digital ph meter, some up and down and check your water after you add your nutes and adjust the ph to about 6.5/6.8... if your ph gets to far off, it can cause nutrient lockout and the nutes will not be able to be processed by the plant.. i hope that this helps you out some..