Well, to start your own manga, you'll need to have your story well plotted out and have your ideas for future events jotted down, you need tou have stable character profiles with all of their information and draw them out and whatnot, after you have most of your story done you'll need supplies, unless you plan to do a web manga/comic. To start your manga you'll need manga manuscript paper, screentone (if you like screen tone), and tone burnishers if you want screen tone, technical pens or pigment liners, markers (copics or prisma color or cheaper ones with VERY good quality), ruler (not the bendy ones, steel is good), and other things. There might be some that i'm forgetting but you'll need those in mind. Oh, and it may not be a good idea to put out all of your charcters and story title online if it isn't copywrighted. People like to steal lol. Hope that i'm of help. ANd you can ask if you need to know anymore.
AAAAAND, well by computer, well i'm not sure about that ; best of luck~