I'm guessing using computer/browser with the alby extension? I'm going to presume you've read this...

https://blog.getalby.com/the-2-minute-alby-guide-to-nostr/

Once the extension is installed and setup, navigate to one of many nostr websites found at https://www.nostrnet.work/ - Upon entering any site you should be prompted by alby to sign an event. Click remember my choice to save time in the future, and click sign/next. Now look for the lightning/zap icon on peoples profiles or on their posts or comments and give it a click...

If you have sats on your alby wallet you should be able to send them! Feel free to reach out on DM if you need any help!