To backup your wallet:
1- Open your Wallet
2- Click on Settings
3- Click on "Show seeds & keys"
4- Write down your Wallet Mnemonic Seed, Secret View Key, Public View Key, Secret Spend Key and Public Spend Key
5- With that details, you can recover your wallet any time.
Another option is:
- Locate the folder where you download the wallet
- Find the .wallet file
- Copy it to the location of your choice for backup