If you are on a per-user plan then you can increase your licenses any time on a pro-rata basis by following the given steps;
1. Log-in to your panel from https://dash.intueri.io and then go to Billing
2. Click on the change plan button given on the right side.
3. Click on "Renew subscription" link given on the top.
4. In "Renew Service Now" check the wallet balance and amount required.
If you have enough balance in your wallet then the subscription will be renewed instantly or otherwise, it will ask you to add funds in the wallet first.
Once the funds are added to the wallet you can follow the same steps to renew the subscription.
To add more licenses to your account please check this guide.