Select a device to use as a MIDI clock source. Drum machines and sequencers work well as MIDI clock sources. Some Digital Audio Workstation programs can function as master MIDI clock sources as well. If you use your DAW in this way, make sure other computer usage is minimized. If your computer is running a variety of other processes, this will likely have adverse effects on the regularity of the clock signal.
Connect your MIDI clock source to any devices, which will be used as slaves. Connect a MIDI cable from the MIDI Out port on your clock source to the MIDI In port on your slave device(s). If you are using a computer, you will need to use an interface for converting between USB and MIDI. If you are using more than two devices, you will need to use a MIDI interface with enough MIDI out ports for your devices.
Turn on your MIDI devices. The order in which you do this is not important, as the clock source does not transmit any sort of locational information.
Set the master clock source device to internal clock control. Depending on your device, this may be a button, or it may be located within a menu. The master clock source transmits pulse signals according to its tempo. As you vary the tempo of your clock source, the other devices should follow.
Set the slave devices to accept external clock control. Again, this may be a button or it may be a menu. Consult the manual of your device if you have trouble finding this function.