We could give you better advice on how to use your 'scope if you would tell us which model Tenma you purchased. There is a huge range of features available on most oscilloscopes, depending on model, but virtually all "modern" 'scopes feature a linear, triggered, horizontal sweep with adjustable sweep rates from microseconds per horizontal division to seconds per division.
Better 'scopes offer a calibrated horizontal sweep, so if you can display one cycle of the waveform, the time for one cycle can be measured by the length of the sweep from beginning to end of that cycle. The reciprocal of this period measurement is, of course, the frequency of the waveform. Accuracy to about two significant figures is reasonable, so the oscilloscope does not replace a frequency counter but it does get you into the ballpark in terms of measuring frequency.
Very important to triggered-sweep oscilloscopes is the accuracy and stability of the trigger settings. Very seldom will you be interested in just one or more complete cycles of a waveform. Instead, you would like to inspect a short time interval of the waveform, one that is particularly important to your circuit operation. This means your trigger must occur very near the beginning of the interval you want to inspect. Often the only way to accomplish this is to use a delayed trigger. A repetitive point on the waveform is used to initiate the delay. After the expiration of the delay interval, the actual sweep (the portion displayed on the CRT) is either triggered immediately or it is triggered according to your selected criterion of amplitude and slope (positive or negative) of the waveform.
It can get a lot more complicated, but that should be enough for your consideration right now. Tell us the model number of your 'scope and what you expect to "see" with it. As
@BobK said in post #11, using an oscilloscope is like suddenly gaining sight after being blind. It opens up a vast array of test procedures that simply cannot be accomplished in any other way. I use my 'scopes more often than my multimeter, although both have a place on my bench. Oscilloscopes "look" at the dynamics of circuit operation, while other devices mostly are useful only for examining steady-state conditions.
