There is a range of different benefits and tax credits that you might be entitled to, depending on your specific circumstances.
Some benefits are based on the national insurance contributions you have paid. These include contribution-based Jobseeker's Allowance, Incapacity Benefit, or Employment and Support Allowance, and maternity benefits.
Other benefits are means-tested, so what you can claim will be based on the existing household income coming from your partner's job. These are designed to top-up income you already have, so you do not need to have paid national insurance contributions to claim them.
Depending on your reasons for being out of work, you may find that you are entitled to income-based (means-tested) Jobseeker's Allowance, income support or income-related Employment and Support Allowance. You and your partner may also be eligible for the Working Tax Credit, especially if you are bringing up a child or suffering a disability.
This is a payment to people working on low incomes to help them make ends meet. So whether you qualify will depend on your partner's earnings. Again, if you are bringing up a child you may be entitled to the Child Tax Credit.
Other benefits you may be able to claim include Housing Benefit, which can help with renting costs; and Council Tax Benefit. All these are available to those who are on a low income or are unemployed.
Finally, because you have been out of work for a while you may be able to claim some back-dated benefits, though in general you won't be able to claim for more than three months. Making a claim for back-dated benefits can be complicated, though, so it's worth getting some one-to-one advice before you start.
You can call National Debtline on 0808 808 400, the Jobcentre Plus helpline on 0800 055 6688, or use the online benefits checker at turn2us.org.uk.