The main menu (`Welcome to Monero` screen) will open. At the bottom left, click on `Change wallet mode` button, and on the next page select `Advanced mode`. Next, open your walletfile again.
In `Address` you should fill the address of the remote node that you want to connect to. This address might look like `node.moneroworld.com` or it could look like any IP address.
In `Port` you should fill the port of the remote node. If a remote node is listed as `node.moneroworld.com:18089`, the address is `node.moneroworld.com` and the port is `18089`. The default port is `18081`, but it can vary depending on the node you are connecting to.