You manage the token purchase choices for your clients within the Tokens Purchase price plan item of each fee base price plan within your system once you have installed/enabled the tokens addon. You would manage that here in the admin tool:

PRICING > [EDIT] Next to fee based price plan > COST SPECIFICS > TOKENS PURCHASE (price plan item)

You first find the fee based price plan you want to setup purchase choices within the PRICING > PRICE PLANS HOME admin tool as shown below:

Then select the COST SPECIFICS admin tool:

and then go to the Tokens Purchase price plan item as shown below:

Within that screenshot you'll add more token purchase options by filling in the fields:

1. number of tokens this option will have
2. the cost for the number of tokens you set above
3. the time from purchase of the tokens when those tokens will automatically expire
4. click here after filling in fields 1-3