Ferrite bead attenuation frequency
I understand that using a ferrite bead attenuates high frequency
currents and can help reduce EMI.

Correct. They act as a high resistance series block at high frequencies usually in the range 30 MHz to 3 GHz. Some will be more targeted at lower frequencies and others will be targeted at higher frequencies. Some will attenuate more; some will attenuate less: -

Their choice depends on your application and what you want them to do. You have to decide why you are contemplating using a ferrite bead. That comes first i.e. what is the problem that makes you think a FB is required? Start with the problem you are trying to solve.
Here's a good article on FBs produced by Analog Devices Inc. Here's its equivalent circuit as shown in that article: -

And here's another section of that article that details the impedance properties of a TDK MPZ1608S101A and 10 nF shunt capacitor. It shows different scenarios of connecting them with a damping resistor should the low frequency resonance be too problematic: -


how does one go about determining this frequency band?

This partially comes from experience and partially comes from EMC lab results that indicate emissions or susceptibility to emissions is too high.

I'm confused about how to select the frequency range that should be
attenuated.

This also partially comes from experience and also partially comes from EMC lab results that indicate emissions or susceptibility to emissions is too high.

is the bead more about suppressing currents that are picked up from
interference from other devices?

A ferrite bead can be used for suppressing interference that might affect other equipment or for suppressing conducted emissions from other equipment affecting your circuit. An FB can also be used to suppress locally generated EMI affecting other parts of your circuit.