UK voting and ID for elections on 4 May 2023 in England and Wales and Scotland, and 18 May in Northern Ireland. I'm still seeing significant misinformation about this so here's information for England, and you can check the same website for the rest of the UK (iirc Wales and Scotland are similar and N.I. is a law unto itself).
1. First register to vote with your local authority. Deadline depends on whether you also need to apply for ID so do this as soon as possible.
https://www.electoralcommission.org.uk/i-am-a/voter/register-vote-and-update-your-details
2. If you have government photo ID and intend to vote in person at a polling station then check if it's valid. Deadline depends on whether you need to re-apply for ID so do this as soon as possible.
https://www.electoralcommission.org.uk/i-am-a/voter/voter-id/accepted-forms-photo-id
3a. If you don't have current government photo ID then the best way to ensure access to a vote is to apply for a postal vote but you need online access, and a printer, and access to a post office (or hand delivery to its destination). Deadline 5pm 17 April 2023.
https://www.electoralcommission.org.uk/i-am-a/voter/apply-vote-post
3b. The government ID linked below is another option for in person voting at a polling station but you need online access, and a digital photo, and a printer, and access to a post office (or hand delivery to its destination). Deadline 5pm 25 April 2023.
https://www.electoralcommission.org.uk/i-am-a/voter/voter-id/applying-a-voter-authority-certificate
3c. You can also vote by proxy, but this is more complicated and most experts advise against it unless you have no other option. If you can't find out for yourself how to do this then it's probably not the best method for you.