Looking for an online course

I work for a company with expertise in electromagnetics physics, specifically dealing with time domain-based simulation software. We routinely need to transform our results into frequency domain, which we do performing FFTs, but we often need to manipulate our data in order to get valid frequency data, and our knowledge of digital signal processing is somewhat lackluster. For example, we may want to do more with windows to address some of the peculiarities of our simulation results, and we would like to learn more about it. Or we may need to interpolate and/or decimate very unevenly-spaced data sets, and we don't want to accidentally mess up the frequency domain results by doing so.

I am looking for an online educational resource that can be used for internal training. A lot of courses I find are very theoretical. For example, this MIT course is certainly very rigorous, but we probably don't need to learn the intricacies of the z-transform to know how to properly apply a flat-top window to our data sets. On the other end of the spectrum (pun intended) are many courses on youtube/coursera, or similar, which might touch upon subjects more directly applicable to our needs, but come with a lot of unknown about their quality.

Could anybody recommend any course which strikes a good balance between theoretical knowledge and practical use, which can be followed online? Free or not. I can provide more details of what we are looking for if my description was too vague.

Thank you very much in advance!