I'll guess that the user manual doesn't have much info on oiling.
Machines that have sat unused for a long time typically have areas within that should move but cannot, as the oil has garnished over time.
In no particular order:
Gently try to turn the hand wheel. If it doesn't rotate, there are spots gummed up/stuck within. Typical areas include the "nose" of the machine, the area under the bobbin, and the zig zag mechanism.
Turn/slide all the appropriate knobs and levers. If they don't move, don't force. Something is gummed up/stuck in the internals within.
Take off the top and check for cracked gears.
Take off all the covers. There is usually a sequence, right side, motor cover, back side, top, nose (or nose, top), bottom. Keep the screws with their cover. Check for plastic/cracked gears.
Clean/remove any lint and dust.
If no cracked gears, proceed with sewing machine oil. Place a drop on every "junction" where there should be a sliding action, a rotating action, etc. i like to turn the hand wheel after every drop. Repeat as needed.
Be careful not to over oil and avoid the motor!
If there are cracked gears, I would abandon, and find an older machine with metal gears. 1950s-early 1970s vintage.
Good luck!