You’re giving Tectonic a try and it turns out that its base “bundle” of LaTeX files doesn’t include a certain package that you want to use. Or its version is too old. Or you have a custom package that isn’t part of TeXLive at all.
At the moment, Tectonic’s support for this sort of scenario isn’t as nice as we would like it to be. But, you have options. This thread lays them out.
Copy the package files into the directory containing your document
This is the simplest answer, in a certain sense. If a certain file is missing from Tectonic’s bundle, you can just put a copy of it next to your main document file. If the package you need involves multiple support files, it is generally fine to just put them all next to your input file in the same way. This starts getting messy at a certain point, but it’s a simple and effective solution in a lot of cases.
File an issue against the
The default Tectonic “bundle” file is built using scripts that are maintained in the tectonic-staging Git repository. If there’s a package that you want to use that’s in TeXLive but not included in the default bundle, it may just be an oversight. If you file an issue we’ll look into it.
Create your own alternative bundle
This one is for advanced users only, and in fact is not really documented well enough to be feasible just yet. But in principle, there’s no reason that you can’t use the tools in tectonic-staging to create your own bundle file that contains whatever customizations you need. You can then make it available on the Internet or access it as a local file.
We intend to flesh out the infrastructure and documentation to make this a more practical option in the future.
Tell us why none of the above will work for you
If you don’t feel that any of the above options address your needs, we’d like to know why! Please let us know in this thread. Tectonic might not be the right tool for you right now, but we’d like to make sure that it can be at least as useful a tool for TeX users as any of the classic engines.