Configure TL-WA5210G as Client mode or AP client router mode. Steps are shown in these FAQs.

[318] How to configure my TL-WA5110G or TL-WA5210G to work on Client Mode
http://www.tp-link.com/en/faq-318.html
[289] How do I configure TL-WA5110G/TL-WA5210G to wireless AP Client Router mode?
http://www.tp-link.com/en/faq-289.html

But it depends on the hotspot's settings whether it works or not. Since you said you have the username and password, the hotspot must be a portal hotspot. Some hotspots have authentication restrictions, as a result no access point can connect to these hotspot to pass on the web authentication.

Thanks radvd. I will try those links.

I am trying to understand these WiFi terms.

You say "Some hotspots have authentication restrictions, as a result no access point can connect to these hotspot to pass on the web authentication."
If you don't mind, what is an authentication restriction?
When you say "access point" that would be my TL-WA5210G?
And what is the "web authentication" the access point can not pass slong?

I can connect to this hot spot with my tablet, and the hot spot is in a park - public campground.

Thanks

I can connect to this hot spot with my tablet, and the hot spot is in a park - public campground.

Do you need to enter username/password in a certain website when the tablet is connected to that park wifi? If yes, the park wifi is using web portal authentication. And I mean this kind of public wifi sometimes has special restrictions that prevent any access points such as your TL-WA5210G to connect to it. Even if you can connect to it, you cannot open anywebsites.