I presume you want to prioritise it over a WAN link ?
Use basic priority queueing for this. It is simple to implement, and it has least impact on the performance of the router, or the other traffic. You use an access-list to define the traffic you want to prioritise, and apply the queue to the interface. You can find several examples on the Cisco website, if you search for Priority Queueing.
You probably also want to do fragmentation and re-assembly, which breaks up the large data packets, so the small VoIP ones don’t have to wait for these to be sent over the WAN. Useful if the WAN is slower than about 2MBps. This should also be found in the examples on the website. However do NOT do this if the total of all WAN links that use this technique are over 2MB/s as this will have a huge impact on performance.