Hi,
Not using the Payment plugin, but you can do it this way:
1.- Create a file with extension .sql using a text editor with this content:
SET @user = 7;
SET @credits = 200;
INSERT INTO /*TABLE_PREFIX*/t_payments_wallet (fk_i_user_id, i_amount) VALUES (@user, @credits)
ON DUPLICATE KEY UPDATE i_amount = i_amount+@credits;
Change @user and @credits values and save.
1.- Import that file on Admin Dashboard -> Tools -> Import Data.
Regards