To get started with tempo runs, start your run with 5 to 10 minutes of easy running to warm up, then continue with 15 to 20 minutes of running about 10 seconds slower than your 10K pace. Finish with 5 to 10 minutes of cooling down. If you're not sure what your 10K pace is, run at a pace that feels "comfortably hard." You can also use your breathing as your guide. For an easy-paced runs, most runners take three footstrikes while breathing in and two footstrikes while breathing out. For tempo runs, you should be at two footstrikes while breathing in and one footstrike while breathing out. If you're breathing faster than that, your pace is too fast.
Even a weekly 15 to 20-minute tempo pace run is enough to get benefits from it, but some more advanced runners will do longer weekly tempo runs of 40 minutes or more.
Also see: 8 Rules for Speed Training