The letter O in braille
dots 1-3-515 of 26⠕
O in braille is dots 1-3-5. O is E plus dot 3.
A capital O has the capital sign, dot 6, in the cell before it: ⠠⠕.
Don't mix it up
Now write it yourself
Tap the dots for O, then Enter. On a keyboard, press F D S / J K L together and let go.
Remember it, don't just look it up
O is in Letters K–T. Braille a Day brings it back tomorrow to answer from memory, then again just before you'd forget. Five minutes a day.