We suppose here that the software to install is software and that the category of the ebuild is category. For example, for TiEmu, software is tiemu and category is sci-calculators.
Here is the way to go:
Verify that you have an portage overlay defined in your make.conf. Generally, you should have:
If they doesn’t exist, create the directories of the ebuild path:
mkdir -p /usr/local/portage/category/software
Download the ebuild and copy it in his directory:
cp software-X.XX.ebuild /usr/local/portage/category/software/
If some patch are provided or other files are joined to the ebuild, copy them to the "files" directory:
mkdir -p /usr/local/portage/category/software/files cp file1 file2 file3 /usr/local/portage/category/software/files/
Create the manifest of the ebuild :
ebuild /usr/local/portage/category/software/software-X.XX.ebuild digest
And now, emerge !