If you received a K-1, that means you invested in an entity that is taxed as a partnership.
A partnership is a pass-through entity and pays no tax at the entity level.
All income, loss, gain is passed through to the partner and any tax is paid at the partner level.
You need to begin to maintain a tax basis schedule of your investment in this partnership as this will be critical in being able to determine if losses are deductible, if distributions are taxable and ultimately your overall gain or loss upon your disposition of this entity.
Bottom line, "yes", you need to include these capital gain amounts in your 2020 tax return and pay any tax as a result of this income. Generally partnerships make a distribution for partners to provide cash for any tax impact. However, that is not always the case.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
