This is not as simple as it should be, but the way to do this is through the command palette (F1 key) and type run task
, it should look like this:

After you click this you will probably get an error in which you do not have a task runner created, you can either press the button or go back to the command palette and edit task runners.
What this will do is create a .vscode directory with a tasks.json file in it, you can either rummage through and uncomment the msbuild section or simply paste this as an override:
{
"version": "0.1.0",
"command": "msbuild",
"args": [
// Ask msbuild to generate full paths for file names.
"/property:GenerateFullPaths=true"
],
"taskSelector": "/t:",
"showOutput": "silent",
"tasks": [
{
"taskName": "build",
// Show the output window only if unrecognized errors occur.
"showOutput": "silent",
// Use the standard MS compiler pattern to detect errors, warnings
// and infos in the output.
"problemMatcher": "$msCompile"
}
]
}
Once you've done that you can edit to your build specifications and either the command palette or CTRL+SHIFT+B will run the builder. Here is the link information for the Tasks: Tasks in visual Studio Code