I am a criminal defence lawyer, and can assist with your inquiry.
I am here to provide general legal information about your situation, not specific legal advice - as per the Terms of Service.
Sorry to hear about the Assault charge. An "assault", in criminal law, is (generally speaking) any sort of intentional physical contact that the other party does not consent to. In your case, the initial information seems to indicate that you feel that you didn't commit any offence, and that your boyfriend called the police, as a result of him being made that you were drinking.
The next step after being charged is usually two fold:
1) It would be highly recommended that you hire a lawyer - whether it be through Legal Aid or privately. A lawyer can navigate you through the criminal court process, which can be very confusing (especially if it's your first time being charged).
2) At your first appearance, the Crown Attorney typically provides you with your "disclosure", which is the paperwork that sets out what evidence they have against you. In your case, which seems to be at typical "he said- she said", it will likely consist of the statement your boyfriend made to the police, as well as the notes of any police officers involved.
Disclosure is important to review prior to deciding what the next step will be. In your case, because you seem to deny committing any criminal offence at all, if you stand by that position after having reviewed the disclosure, the only realistic options then become (a) having a lawyer on your behalf try and negotiate an outcome with the Crown that sees the charge being withdrawn or (b) setting a trial date.
Getting a charge withdrawn is usually the best outcome, rather than having to take a risk by going to trial. However, the Crown Attorney has to agree to this, and they usually only agree where (a) there is no reasonable prospect of conviction or (b) it would not be in the public interest to continue the prosecution.
A charge can be withdrawn unconditionally or on conditions. The latter method is usually a "Peace Bond" resolution, which is a promise of the accused person to the court that they will comply with certain conditions (usually for a year), in exchange for the Crown withdrawing the charge.
I hope this helps.