You already have some credits to start with, but if you'd like to be able to try new things on IMVU, you might want to buy some credits.
Check the Buy Credits Page for information about buying credits, upgrading your account, cool features, and different payment methods.
To begin, choose a payment method. I recommend any of the "bundle" packs, they are the best for a new user.

For now, download the IMVU program and try it out!