This might be trivial but keep in mind that the insertion of the current measurement instrument (likely to be a DMM) may result in a change in the operation of the load - since a slight but measurable voltage drop can result. As already implied - measure the current and voltage - and I would encourage measuring both at the same time (requring a second DMM or other meter).
My teacher in high school taught and demonstrated how to use a multimeter.
My neighbour also demonstrated how to use a multimeter.
Years ago, universities had professors who actually taught the students, not a puppet lecturer who just reads stuff like today.
Students asked the prof questions that were answered by him, not by guys on a forum.
What has become of education today???
There are numerous publications that do a great job at explaining how to make these measurements. The publications may be in the form of a book, journal or magazine article or on-line source. If you are attending a university I would expect the library to have plenty of these publications. I would encourage you to review several of these. They are likely to offer a complete picture with diagrams and explanations that match the diagrams. You might still have a few questions that can be handled by the forum.