lets assume I have some bitcoins in a wallet on bitcoin core and I am going to use zap to send you some bitcoins over lighting, a simple walkthrough from the very beginning till the moment you receive the bitcoins
1. Download Zap and set it up (create a new wallet, write down the seed which can be used for wallet recovery). Wait for Zap to synchronise.
2. Send some coins from your Bitcoin Core wallet to Zap.
3. Click on 'Channels' in the bottom-right corner and select 'Create'. Now you can either use a specific node or use a suggested one. I would recommend you the latter option since it will be your first time using the Lightning Network. Whether or not your payments are going to fail often depend on the node you choose.
4. Once the funding transaction get 3 or 6 confirmations, the channel should appear as active. Now, you should be able to send payments over the Lightning Network by paying the invoices generated by merchants or other users.
Feel free to ask questions if you get stuck at one of these steps. You can also try looking for videos on YouTube. The UI has changed slightly but everything should look similar.