Buy connectors with as many ports (or more) as wires you need to splice together. Cut each wire so they're the same length.

Heat shrink tubing is made of cross-linked polymers, which are polymers in which the monomer units are cross linked together ...

If you've spent any time DIY-ing around your house, you've probably seen wire nuts. They're the colorful, twist-on connectors ...

which is made up of rows of four IDCs that are used to splice pairs together. There are also 110 blocks that connect a punched down wire on one side to preconnected patch cords with connectors ...