You can rename address and account names in settings. Swipe right to left, then
You can not delete addresses and accounts.
You can not currently rename wallets. You must first save any information you want from the wallet (especially the mnemonic seed!), then delete the wallet, then restore from mnemonic seed.
You can delete inactive wallets by clicking on the hamburger menu, then
Wallets, then swiping right to left on the wallet name, then clicking