Switch over to the branch "issue1" when you want to add new commits to it.

Use the checkout command to switch branch.

$ git checkout <branch>

Switch to the branch "issue1" by doing the following.

$ git checkout issue1
Switched to branch 'issue1'

This history tree should look like this at the moment.

Current history

By passing in the -b option when executing the checkout command, a new branch will be created and you will be switched over thereafter. $ git checkout -b <branch>

Once you are on the "issue1" branch, you can start adding commits to it. Let's add the bold text below to myfile.txt and commit the change.

Git commands even a monkey can understand
add: Register a change in an index
$ git add myfile.txt
$ git commit -m "append description of the add command"
[issue1 b2b23c4] append description of the add command
 1 files changed, 1 insertions(+), 0 deletions(-)

Our history tree will now look like this.

Current history