The most common question I see in all of the years I've been a member of this sight is "how much weight should I start out with as a beginner. There is no really good simple answer that involves a number but there is a process that is fairly simple to follow and it will help you to determine the answer that applies to you.
The first and most important thing to understand is that lifting as it applies to fitness is a lifestyle. So you're going to be doing this for a good while, hopefully a lifetime, So getting the correct weight immediately doesn't really matter that much.
The thing that you should be most concerned with is not how much to lift but how to lift. The answer to the how question is that you should learn to lift with perfect form for each lift. That means it's much better to start with lighter weights and perform your lifts until the form is perfect. Once your form is correct, then worry about how much.
If you are doing 3 sets of a lift like, for instance bench press. The first set of 10 is a warm up set so you should be able to do all ten very easily. Add a bit of weight for the second set and again, finishing your set of ten should be relatively easy. The third set should tax you and it should be difficult to finish with good form.
I used ten repititions merely as an example. Different types of workouts call for different numbers of repititions. Worry about that later.
The most important thing to learn as a beginner is your form. You may have to look at the photos of each exercise as you do them so you may need your computer near by. Good form prevents injuries. This is really important. If you injure yourself you may be down for a while and you may just give up.
There is an aspect of proper form that isn't emphasised nearly enough. That is speed. A good lift should be controlled. It is better to lift slowly and drop slowly than to do either quickly. Avoid swinging the weight in order to use momentum to help lift more. You will get more benefit from a slow controlled deliberate lift than a fast, momentum driven lift.
Breathe out on the lift and breath in on the return. This is all part of proper form. Do not arch your back to achieve a heavier lift. Don't hold your breath. Lift fluidly.
If you take the necessary time to learn how to do every single lift with proper form and follow the suggestions I outlined, eventually you will answer the question of how much to lift for yourself. You're really the only one who can answer it. If you're doing this for the right reasons, you'll be doing this for a long time. There is no hurry. Enjoy the trip.