Welcome to the forum. Don't be afraid to ask any question no matter how simple you may thing it is. There are lots of really knowledgeable people on here that will bend over backwards to help you out.
First get a manual for your lathe. That will tell you how to set up your lathe. While setting up a lathe is pretty similar from one lathe to another there may be some quirks for your particular lathe that you will find in the manual.
Mikey's very long thread on grinding tool bits is an absolute must read. I have read it all the way through several times and is my go to source for grinding tool bits. Because you are into milsurp rifles you will need to learn how to grind tool bits for Whitworth 55* threads. Mauser barrels have whitworth threads.
Once you have your lathe set up you will need to practice and more practice and more practice until you develop the motor skills to operating a lathe. I used pvc pipe and fittings to practice on to start with. All you are trying to accomplish is learning motor skills. Practice external turning and internal boring. When this is 2nd nature move on external and internal threading. It does not matter what thread pitch you are using other than to practice with both even and odd threads per inch or the diameter of the pvc. You are just learning the the motor skills.
Once you have the motor skills down pat move on to turning and boring in steel and aluminum to precise OD's and ID's. You mentioned that you only have lantern tool post. A good first project would be making an adjustable spacer for the lantern tool post. See the Winky's Workshop video.
. Another good first project is to make a norman style QCTP. You will get lots of practice with your lathe. For under a $100 in materials you will have a QCTP and 15 to 20 tool holders. You can never have too many tool holders for your QCTP. Lots of forum member have made them. Not hard to make and you only need a lathe and a drill to make the post and tool holders.
https://www.hobby-machinist.com/threads/norman-style-qctp.79705/ It doesn't hurt to have a mill but it is not essential.
Do not and I mean do not buy everything under the sun to start with. Only buy what you absolutely need for the project at hand.
For educational videos IMHO opinion there are none better the Mr Pete's aka Tubalcain videos. He is a retired high school shop teacher and knows how to teach. He is my go to source for learning how to operate a lathe and a mill. There are others who offer lots of good advice and suggestions but Mr. Pete is the best of the best for rank beginners.
Once you get the basics down there are lots of gunsmith specific projects to make. I made a micrometer chamber reamer stop. And a spider for the outboard end of the spindle. Lots of forum members are into gunsmithing and have made all kinds of things to help with their gunsmithing.
Most of all have fun with your lathe.