How do I combine several pension pots? Total beginner here

gm0

Repent.  Start keeping that paperwork with each employment and work down your list to find older ones.  Even if all you do - time limited by other commitments - is to start to gather them up. 

Transfer and merge can improve your investing options, or reduce your costs.  A bit. 
But it asks you to either spend time on it, and/or pay someone to do it for you.
Many of us reach our 50s before this gets off the stack of household chores.

For DC pensions (A saved up "pot of money" pension in english).  Can be moved.  Or moved in with others i.e. merged.  So that 3-5+ become one. 

This comment excludes discussion of final/average salary pensions - so called defined benefit (DB).  A more involved topic.

DC Pension transfer is free.

And this is something you can do yourself with a few clicks and phone calls. And perhaps the odd form or two. 

But it requires time to find paperwork and membership numbers. 

AND time

To shop for a new provider

To select how your "merged" pension will now be invested from now on (Picking a fund, a risk level or funds)

And to do some form filling with the new provider - to pull the pension across.  Transfer works on a pull model.  Like moving an ISA.  You don't tell the old provider to move it or close it. You tell the new one to pull it across. 

To do that you need to tell the new provider who the old one is and provide enough information to find  you.  NINO obviously.  And also roll numbers/staff numbers as may directly point to your account.  Current address. And "last known to them address" for the old provider (if you failed to tell them you moved) may also be helpful data.

Examples of people who market consumers DIY SIPPs are AJ Bell, Fidelity, Vanguard, iWeb, HargreavesLansdown.

If that sounds like a lot to work through.  Then one of the firms that organise transfers and merge pensions can do some of the admin of it for you. For a fee naturally.  Some of that fee will be upfront.  And some will likely be baked into a higher price pension product that they put you into. 

One (not recommending it particularly as I haven't used it) example of this type would be PensionBee who seem to specialise in marketing pension tidy up and merge.  And offer some simplified investing options.  And do some hand holding.  It is not especially cheap but it seems to meet a need. People have generally fed back fairly positively about the handholding aspect. Search the forum.  Handholding is not something you get with the basic DIY SIPPS listed above. 

Financial advice is a regulated activity with strict liabilities.  People who are not selling it. Do not wish to stray anywhere near it.  So being helpful about your individual circumstances via guidance is not something most of these companies doing basic transactional products stray into.

An Independent Financial Adviser can help.  If there are sufficient assets for your case to be of interest to them at a sensible price to do the work for you.

If you get help - they will want to know where you worked, what schemes you were in, personal details. etc.  So the making a list and identifying them part doesn't go away entirely even if you want to buy the "setting up my merged pension" part.

With any old pension - before transferring it you really do need to examine whether this pension is good or bad value as is.  How it is invested. What it costs each year.  And if it has any (older schemes especially) special features which make it worth staying in.   This step should not be skipped.  Old can be bad, expensive and limiting (when you get to access age especially).  But it also can be cheaper than current market offers.  So it is not possible to generalise that you should always or never move and merge.   In rarer cases there are older features which mean it should not be transferred at all - the special terms are removed when you move the money and do not travel with it to the new provider.  Examples of this are guaranteed annuity rates. Higher % of tax free cash.  Earlier retirement age.

Good luck.

As to the dashboard.  Don't hold your breath.  This has been a very long road already.  I remember talk of it >15 years ago in civil service pension circles.  And here we are.