See https://github.com/haikuports wiki pages.
Haikuports is our repository for software ported to Haiku, it rely on our porting tool, haikuporter.
Porting can be as easy as duplicate a sample recipe file, edit it to change summary and description texts, point source url to what you want to port, putting some "make" in INSTALL() function and try how it goes.
But most of the time it requires a bit of skiils on how many softwares are built, either by autoconf tools + make, some are using cmake, some have their own build system, some don't need to be built but the set of files already ready often still need to be adapt to map Haiku platform expectation regarding their location on disk, etc.
There is very good two parts tutorial "how to port" available in the wiki. Read it, try it.
And for there more complex things, you'll find help regarding haikuports on IRC, #haiku channel.