Ok im not 100% clear on what your saying.
Are you confusing Ph Calibration fluid with ph up/down fluid?

If you have calibration fluid,dip the tester(meter) in a cup of it and adjust the screw or dial on the side of the tester until the screen reads whatever ph number your calibration solution is ( usually 4).
Or use your tap water and adjust it to 7 if you know your tap water is 7.
And yes never reuse calibration fluid.
The packet of calibration fluid that came with you tester is only for 1 use,Its not pricy to buy and you can get it in any head shop or online.