After you install a wallet, you need to get some Monero. There are multiple ways to acquire some coins to spend, like mining or working in exchange for Monero, but the easiest way is to use an exchange and convert your fiat money into XMR. Many exchanges, centralized and decentralized, list Monero (XMR).
The community has put together a vast amount of resources and documentation. Users can find useful info and guides about common configurations andtips in the 'User Guides' section. Developers can find everything they need to build a service based on Monero or simply communicate with the networkin the 'Developer Guides'. The Library offers publications and books downloadable for free, including the full 'Mastering Monero' and 'Zero to Monero' books.