For very basic model making, try tinkercad, it runs in your browser and gives you some basic controls to make objects.
Knowing what printer you have might allow others to give you advice, some printers behave differently than others in terms of hardware and system software.
What is your goal for 3D printing? Are you looking to print random knick knacks, functional prints, or just experiment?
Printers vary a lot in what they can do and their user-friendliness. You can go from simpler, almost plug and play models to more complex ones that require much more tinkering. They also vary a lot in price from a few hundred to thousands of dollars.
Modeling: YouTube is helpful here search for AutoCAD (computer aided design), mid journey actually has an unreal render I hope to export soon and ai is getting better and better at generation.
Buying a printer: 2 main categories plastic and resin. Plastic is easier, larger scale, generally printed in pla petg or abs each with their own qualities. Resin is generally smaller and more precise(read jewelery minis), and requires requires UV treatment/chemicals to cure.
Early recommended printers: (plastic) ender or prusa. Ender will be more maintenance and give you better tuning/control, prusa will be more expensive and work a bit better out of the box.
Material: highly recommend just starting with pla and when you figure out the basics, you can change materials. The other ones will last longer and survive longer, but 3d printing has a learning curve. PLA is a good introduction
First print: download the STL or model of a benchy, it may be tempting to print something cool first, but this is a tool that needs calibration. Benchies have specific dimensions to print angles, rings, platforms, bridges ect). Go download software of choice, 3 years ago that was Cura. Load the STL file and you can click around, but I don't recommend changing much. PLA prints well around 200*, I liked to add 2-4 extra layers of "shell" for durability, hollow support TREES are fantastic for overhanging ledges - NO COLUMNS!!, 20% infill means it will be mostly hollow but print quick and have some structure. Cura would default to the most geometrically sound pattern (honeycomb). A raft will put a grid down first to stabilize, it helped day 1, but got in the way later.
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3d printing is a lot of work, plastic deteriorates over time, but you can do a ton of cool stuff. I recommend finger surfboards, organization kits to start and the replica jet engine is a right of passage.