Midi tracks on Cubase are tiny, tiny specks on the machine resources. You seem to have got very confused here and entering notes in Cubase can be done in step time - probably the most old fashioned 80's method, or you just draw them on the edit screen - but you have to do a few things first.
Start with creating a new MIDI track. Set the markers to however many bars you work with comfortably - so maybe 8,16,24 - something like that. With the cursor, double click on the empty space next to your new bidding track - below bar 1, and an empty midi track appears the length of the section you picked - so let's say 20 bars long. Double click it and the editor appears. Up at the top to the right you will see the quantise box and it will probably say 1/1. If you right click to select the pen tool, then a note you enter will snap to the nearest bar line and put in a note lasting the entire bar. Change 1/1 to ¼, and it will put in quarter (crotchet) notes. With the snap button off, the notes can be placed anywhere, and with it on, only at bar divisions you set in the Q window.
Sound wise - I assume you've fathomed out how to make sounds play?
You can drag left and right in time and up and down in pitch, but one handy feature is the key to the left of the space bar - if you hold it down, then drag a note, then you can copy, not move notes. You can use this with groups of notes too - so if you want to repeat 8 notes, highlight them, then press that key and create another 8 notes.
Copy and paste, dragging and manipulating the notes is a primary thing to sort out - and it can become very quick. If you are creating a bass part that goes dum-de dum, then do one bar, copy it over and over again, then when it needs to change notes, go back and move them. This I think is why step entry - a system where notes are automatically put in one after another automatically at the Q setting tended to fall out of use. Don't forget mouse entry puts every note at the same midi velocity so while great for dance and 80s music, it sounds horrible on real instruments. Below the editor you can see the velocity of each note, you can edit those with the mouse too. It will kill you, but you can.
If you put in all ¼ notes, then again with the mouse pointer, you can make them longer and shorter - this works on one note, or groups of notes. Does that move you forward?
