How can I help my boyfriend in getting his residence visa?

You could ask yourself whether this man is dear enough to you that you would marry him. If he entered the U.S. legally, with a visa, and now became your husband, you would be able to file an immigrant petition for him Provided that: a) your husband-to-be has no criminal record, and was not ever in trouble with the immigration authorities; b) your marriage is real, not just to "get him papers"; c) you have income over $19.5K a year or have a co-sponsor who would sign an affidavit of support for your husband; and d) all the paperwork is done right, - then he should have work permit card in about 90 days, and a green card in about 8-10 months.

You have to marry him.

If your boyfriend is now in the US, you must first marry him and after which, you can file a Form I-130 petition with CIS concurrently with his Form I-485 application for green card. If it is properly done, the entire process from filing to joint interview at your local USCIS office leading to his green card, should take no more than 6 months. I must caution that not everyone who applies for green card succeed and that there are several requirements for filing a good application. They are too many to discuss in this forum especially without knowing more about your intended husband.

It's important to know how her entered the US. With a visa?