First I would google for some basic github / git tutorials, there are a lot =)! Then you will understand hopefully what I'm saying next:
1. Fork the original repository
https://github.com/jgulledge19/Slideshowmanager to have your own "copy" in your account.
2. navigate to that forked repository in your account and copy the clone url in the right sidebar
the next steps i'm explaining for osx/bash but should work with windows the same if you're set up correctly
3. create a folder somewhere for your github repositories, e.g. usr/github/, then go to your command line and go to that folder, e.g "cd usr/github/" then you clone that repository to your local machine with "git clone <thecloneurlyoucopiedbefore,withouttheseparentehis>", if it worked you should now have a new folder "Slideshowmanager" in the github directory, this is your local repository
4. again in the command line do "git checkout -b <branchname>" to create a new working branch, there you will make your changes / fixes you'll commit later...
5. make the fixes in the code
6. go back to the command line (always in that git repository folder!) and do "git status", it should show you which files were changed
7. then you can do "git commit -a -m "your commit message"" to add all modified files and add a comment on what you changed with that commit
8. now you're set up to push your changes to your online github repository with "git push origin <branchname>" -> this will create a new branch in your online repository...go there and you'll see a green button top right saying "compare & pull request", click that, check if the changes you made are correct, comment it a bit and click "send pull request"
9. that's it so far, the original author now has a PR in his repository which he can merge or not...
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futher helpful things:
if you maybe want to edit something after your fixes were merged, it's important you sync your own repository with the original one, you can do that by going via command line to your local repository folder and do
"git remote add original
https://github.com/jgulledge19/Slideshowmanager"
that will add the original repository as a "link" to yours, the term "original" you can change to whatever you like, I have seen many devs doing it as "upstream"...
be sure to switch back to the main branch, this is mostly "develop" or "master" depending on the original author, you do that by
"git checkout master"
then you can merge the changes from the original repository with your master (or whatever branch) like
"git merge original/master"
then push the most recent version to your online repo with
"git push origin master"