I am not an expert but I did some synastry readings and I learned a thing or two... there is plenty of stuff about Astrology in the forums that will help you down the road.
First of all, to be able to interpret synastry you need to be able to fully interpret the birth chart. The way you do synastry readings is by overlapping the two charts and then interpret how the planets interact with each others. You can do this manually if you're skilled enough to calculate the degrees, or you can use this website to calculate them for you:
https://horoscopes.astro-seek.com/synastry-chart-online-calculator
Keep in mind that this website will generate "interpretations" which are bogus. This stuff may or may not make sense depending on the nature of both of the charts, this is no different than getting your chart read in any other generator out there. You will have to go through all of it yourself, because there is much more to Astrology than merely interpreting the aspects. You have to take into consideration where these aspects are happening (houses), degrees, angles, fixed stars and everything else you normally would with a birth chart.
If you want to analyze whether or not someone is compatible with you, you also need to read their chart separately. Because the nature of their chart will come into play as well, how an aspect will manifest will depend on how the planets involved manifest in the lives of both people. For example, you may have an harmonious aspect with someone's Venus, but if their Venus is conjunct a malefic star, that is going to influence that interaction into a whole new level.
There is a lot of synastry advice in the JoS Astrology section, go through it when you're reading the charts. Do not ignore the red flags. I unfortunately did so very recently because I was convinced that it couldn't be that bad, and it definitely was as bad as HPS Maxine said it would. So if you see that you're not compatible, someone has a messed up chart that would be harmful to you in any way, just walk away without hesitation, don't try to make it work because you're only going to waste your time and energy, in theory it could work in time with the right workings, but these are very powerful forces that you don't want to mess around with specially if one or both are not powerful enough, there is no point. There is someone out there who is effortlessly compatible with you.
What I usually look for is nice aspects involving Venus, Moon, Mars, conjunctions and so on, also Neptune, but that again would depend on the nature of everyone's Neptune, it could get fantasy-like with the wrong Neptunes... or it could get spiritual and mystical. Jupiter is also a good one to look for in nice aspects, given our religious nature. Aspects to the Sun and the Ascendant are also important.
Check the Vertex and the North node as these are about fate, look for conjunctions with personal planets. The karmic planets are also indicators of fated relationships.
From my experience, fated relationships specially the ones that have a lot of karmic aspects involving Saturn and so on, are not necessarily "the one". If that's what you're looking for anyway. A relationship may be fated, but that doesn't mean it is the best for you. It is usually the universe aligning you with something that you would normally attract depending on your own karma, and that may be something you need to learn or overcome. If in your own birth chart you have a messed up love/sexual karma, you should do one or more workings to get rid of that first, because whatever is in there is what you're going to attract in the form of fated relationships which may not be healthy for you. HPS Maxine has written about it, and so did BlackDragon666 and probably others.
About your second question, if you're using more advanced techniques to read the chart of a jew, such as in meditation, you probably want to clean your aura an your chakras afterwards. But you can definitely study it, there is nothing stoping you from that, you shouldn't be afraid of anything like that because you have the tools to do it safely. You'll usually see mental illness, evil intentions, a lot of conjunctions with malefic stars that make one violent, greedy, take advantage of others, and so on. It is interesting, because you can see in depth how Astrology really does have the answer for everything.
It is not much but I hope it helps.