I am trying to boot Ubuntu on my computer. When I boot Ubuntu, it boots to a black screen. How can I fix this?
Use the latest version of Ubuntu
Other answers here are very good, but one point that deserves emphasis is that, as a general rule, you should use the latest version of Ubuntu, or at least the latest long-term support (LTS) version. Ubuntu, like all OSes, relies on drivers for video (and other) hardware, and these drivers often lag hardware introduction. That is, if your computer was introduced as a new model in 2016, it may include hardware with no support in Ubuntu releases prior to that year. Even when hardware is supported, there may be bugs that might be fixed in a more recent release.
Ubuntu release numbers are dates -- 16.04 was released in April (04) of 2016; 16.10 was released in October (10) of 2016; 17.04 was released in April (04) of 2017; and so on. New versions of Ubuntu appear every six months.
The April releases in even-numbered years are long-term support (LTS) versions. Like other releases, these see kernel and X Window System version updates. Starting about three months after the initial LTS release, and every six months thereafter for about two years, new point releases appear for LTS releases. These point releases incorporate the kernel and X updates from the previous release. Thus, 16.04.1 uses a (slightly updated) kernel and X from 16.04; 16.04.2 borrows these components from 16.10; 16.04.3 will use these components from 17.04; and so on. A total of five point releases are made available for LTS releases, after which point you'll need to upgrade to a newer Ubuntu release if you need new major versions. (There may be bug fixes within a kernel or X series, but not updates to new major versions.)
Thus, if you have particularly new hardware, you may need to use the very latest release, even if it's not an LTS release; or if you insist on an LTS release, you may need to use the latest point release in its sequence. For very new hardware, though, you may need to wait or track down bleeding-edge drivers that may be difficult to install.
Note that non-LTS releases are supported for just nine months; but LTS releases are supported for five years. Thus, it's generally best to stick with the latest LTS point-release, if possible; but you may need to use the latest non-LTS release, or even a beta version of an upcoming release, to get the very latest kernel and X Window System.
If your hardware is older, you may be able to use an older Ubuntu version; but as I've already noted, the newest version may incorporate bug fixes that can help resolve problems, even on older hardware.
If you installed from a USB drive, check whether it boots with the flash drive plugged in and if so, this may help.