Translate the sentence 'Iris ad Romam ire volebat ut multum cibum cenare posset.'

Simple answer: 'Iris wanted to go to Rome so that she could eat lots of food.'

Explained answer: We first identify the subject, which is 'Iris', and we know it is the subject because it is in the nominative case. We next have to look for a verb, and we find there are two: 'ire' and 'voluit'. 'Ire' is an infinitive, so we turn to 'volebat' as our main verb, which is the 3rd person singular imperfect tense of 'volere', meaning 'to want'. So we translate this as 'was wanting' or 'wanted'. Now the infinitive makes more sense after 'volebat', because the phrase means 'Iris wanted to go'.
'ad' indicates movement towards, and takes the accusative case - and 'Romam' is 'Roma' (Rome) in the accusative case, which works perfectly! So the whole first part of the sentence means: 'Iris wanted to go to Rome'.
Then we have an 'ut'. 'Ut' signposts a whole range of subjunctive clauses, so this could be a result clause, a purpose clause or an indirect command (it can't be a command here because there is no verb of ordering). There is no signpost word like 'tam' or 'tantus', so it can't be a result clause, and we can assume that it is a purpose clause, and we translate 'ut' as 'in order to' or 'so that she...'.'Ut' takes subjunctive, so we look for a subjunctive at the end of the sentence, and find it in 'posset', which is the imperfect, 3rd person singular subjunctive of the verb 'posse' (to be able to). We can translate this as 'so that she was able to' - and then take the infinitive 'cenare' after this to mean: 'so that she was able to eat'.
After the verb we then want to find an object, in the accusative tense, and there we have 'cibum', meaning 'food'. 'Multum' is an adjective meaning 'lots of' and it has the same case and number as 'cibum' and so we can say that it agrees, to mean 'lots of food'.
Thus we can put all of these parts together and translate the whole sentence as: 'Iris wanted to go to Rome so that she could eat lots of food.'