OH my God! ph for soil plants should be 6.5 5.8 for hydro. This can vary, but it is pointless to vary if you don't know what you are doing...there are reason's and times to vary the ph.

buy bottles of ph up/down...mix with your water. let it sit for 20 minutes ...put the runoff in a glass and test the ph. but, I usually just keep my water at 6.5 and everything grows great.

as for lime. It is called crushed dolomitic lime...It is to be mixed somewhat like mention above. It buffers the soil ph to keep it consistent. You just mix in soil. once or 2wice if you repot.
It also adds needed magnesium to your soil.

hope this helps.