1. Check with your local government/HOA regarding restrictions for STRs. Check regulations around fire, electricity, boilers, gas and make sure you have appropriate certification. Also take out home insurance for short term rentals and instal CCTV or similar if you host remotely.
2. If you lease make sure your landlord allows STRs.
3. Read Airbnb Help Centre and the tutorials on this forum for the basics around how Airbnb works.
4. You can keep financial records around income and expenditure on an Excel spreadsheet or similar and keep all invoices/receipts
5. Check with your tax office regarding how you file taxes/declare this income.