Your widget is another project, along with the main application that runs the widget, in your workspace. So you need to install Alamofire in one (or both, depending on your needs). Change your podfile to following code:

source 'https://github.com/CocoaPods/Specs.git'
platform :ios, '9.0'
use_frameworks!

target "MainAPP" do
    pod 'Alamofire'

end
target "Widget" do
    pod 'Alamofire'

end