‘Tener ganas’ is complicated to translate for our Spanish speaking students in our Skype English classes. The important thing is to use phrases or words that demonstrate enthusiasm. For example, ‘I want to go on holiday’ or ‘I wish to see you’ or ‘he can’t wait to finish these exams’ or ‘We feel like eating chocolate’ or ‘She is looking forward to the meal’ or ‘they fancy eating fish and chips’. In summary, the key is to use a phrase portraying enthusiasm. Hope that helps.