It can take up to 24hrs to activate a SIM but typically an hour. Check your mygiffgaff page for your giffgaff mobile number on lhs and credit on rhs to show it's activated.
Is your sim activated? As in when you login to your "My giffgaff" page can you see your number on the left? and on the right does it show your balance and the goody you are on? If you can see these your sim is activated.
Internet settings need to be entered manually. Follow the guide below:
What phone are you using? If its not an android or iPhone:
Text SETTINGS to 2020.
If its an android phone, go to Android market and download GiffgaffAPN.
If its an apple iPhone, try this:
Try this first:
1) Insert your giffgaff SIM
2) connect to wifi
3) open safari and go to http://invalid.name/giffgaff (it might take some time to load, just wait awhile for it)
4) a notification comes up and asks you to accept a profile
5) press install and then Install now to confirm
Ultimately its a general setting but normally being entered manually for iPhone, they are:
Settings > General > Mobile Network
Connection Name: giffgaff - GPRS
APN - Access Point Name: giffgaff.com
Proxy Server Address: 188.8.131.52
Login - Username: giffgaff
MMS Proxy: 184.108.40.206:8080
Max message size: 2097152
MMS UA Prof URL: just leave blank
MMS port: 8080
APN type: mms
Hope this helped.