The funding payment is reflected in the position's realised PNL field, however, it is actually locked to the position margin and not considered part of the account's Available Balance.
To have the funds unlocked from the position and included in the account Available Balance, you must change the leverage level of the position so that the margin is rebalanced or close the position altogether. The funding payment will then be unlocked from the position margin and included in the account Available Balance (ie, it can be used as margin on other positions.)