Charging multiple laptop batteries
You may not be able to charge multiple cells at once with this charger, unless it features a balancer (or even multiple channels with separate control). If charging multiple cells is supported (which is not uncommon for RC model chargers), then read and follow the manufacturers instructions.

The reason for this is, that the charger needs to know the current in each cell. This is not possible, if you simply put them in parallel.

For laptop batteries, you will likely not be able to charge them at all, unless you rip off the casing and connect to the raw cell. 

CAUTION: Lithium cells may self-ignite or even explode if mechanically damaged or overheated or shortcut. They may do so after a while even if they look OK initially. Several Samsung S7 have melted, just because the battery compartment is a fraction of millimeters to small.

When working with lithium battery cells (charging or pulling current from them), keep in mind that you are dealing with a little device with enormous energy density. This is a property that modern batteries have in common with old style explosives. Its not quite as dangerous a nitroglycerine, but certainly more dangerous than Plasticine.