Offset, you use your ears and line the timing point up with the first downbeat of the song. The downbeat will usually be the first important sounding note. If you start tapping T at the right time it should give a close enough offset but idk, i never use that
You add new uninherited timing points (red lines) when bpm or time signature changes, usually you wont need to though. Dont worry about time signatures if you dont know what they are for now, someone in modding will point it out if you ever map a song that isnt just 4/4 and its not usually that big of a deal. You can wait to learn the music theory stuff until you get a hang of the editor a bit more.
Inherited points, or green lines let you change sv multipliers, hitsound volumes and samplesets, and add kiai flashing. How you use them is entirely your choice.
Slider tick rate just changes how many slider ticks happen per beat (the white ticks on the timeline), 1 is usually fine, but it should fit in the beatsnap divisor the song is on if you do change it.
Base SV just changes how fast sliders move, and what you put it at is your choice, plus you can use green lines' multipliers to change SV at different parts of the song later anyway.